First off, congrats on your weight loss so far and your commitment to lifting!

My advice is to not rush into it too soon. I have 4 kids so it took me a bit longer to get through the book than most people, but I would take the time to read it. The nutritional section is really important too. Take some time to figure your your calories (I compared the book to Scooby, but the book has me lower on a weekly basis, so I'm doing the book calories, adding a healthy snack if I'm hungry, and will eat back some cardio calories, though I'm not doing much cardio currently).

Fish is a great source of protein. Not sure if you eat fish or not. To meet my protein requirements I do use whey protein to supplement.

Do you have access to any DB's at home? This is what I did, and it's not for everyone. I took two weeks to practice and learn proper form for squats and deadlifts. I watched StrongLifts and Mark RIpptoe videos. I also bought Starting Strength, which is awesome for learning form. Within those two weeks, I ran through workouts A and B twice with just DB's, doing A and B each once per week. I continued on with cardio and 30DS. In the meantime, I also went to the gym to figure out where all the equipment was that I needed. Doing the practice sessions at home allowed me to focus on form, have an idea of starting weight, and how things were going to flow at the gym. I always erred on the side of starting too light and added extra sets if I needed to.

Here's a good article on losing fat and gaining muscle at the same time:

http://scoobysworkshop.com/gain-muscle-lose-fat/

It's pretty in line with what the the author of NROL4W recommends.

The book totally neglects stretching, so make sure you have an idea of what your stretching routine will be.

Hey girl - so here's my advice:

1. If you have a smart phone, download the app called "MyFit". It has a nice database of exercises with animations & instructions. Plus you can search them by name, muscle, equipment, etc. The animations made the workout instructions clearer for me (on some) than the book did.

2. The book gives you some sort of guidelines on amount of weights to use, so I'd make sure you read it front to back before you begin, it's a quick read. On any barbell exercises, I'd warm up with just the bar itself, then figure out how much you think you should add on for the workout itself from there. With any dumbbells, just see how you feel after one set. If you think you can do more, do your second set with a little more weight. If you end up not being able to finish the reps because the added weights were too heavy, it's okay - don't force yourself (and I bet you'll get both full sets with that weight on your next workout day!) However, if you end your sets feeling like you could do another set, you probably should have added more weight and should keep that in mind for next time.

3. The book also gives some info on getting more protein but he definitely says it's harder for vegetarians & vegans. Since you are a vegetarian, at least you can eat eggs & cheese for protein. And low fat cottage cheese! And greek yogurt! There is also a protein powder called Brown Rice Protein that I use sometimes (along with the other protein supplements I use). Pretty sure it's actually vegan. But I like it because it isn't "flavored" like most others. I've heard lots & lots of good things about Sun Warrior proteins as well... which again are vegan. And regarding beans, they may be high in carbs... but they are also high in fiber and soluble fibers slow down the absorption of glucose, thus reducing glucose/insuline spikes. Which the main reason you want to watch your carbs is to control your glucose & insuline. Also keep in mind that the best time to eat high GI carbs is after a workout.
Oh also, do you eat seeds? They tend to be a good source of protein. Especially chia seeds.

The book provides a diet guide as well (including how many calories to eat). 900 calories a day is definitely too little. Even 1200 a day is not enough in my opinion. You'll lose "weight" at that point - but you'll likely be losing it in the form of muscle. I think lifting will make you more hungry - you'll need those calories to give your body energy to complete the workouts. But I'm surprised any cardio/lifting that you are doing now isn't making you hungry already. Not that I'm doubting you by any means.
I can go a few days without working out, then eat minimal calories on my first workout day back and be ok. But the day after that workout I'll be STARVING! I guess it may take a bit for your body to adjust but I think it will only take a few strenuous workouts. And maybe a gradual calorie increase? I started back on here in beginning of Jan with 1320 calories (always eating back my workout calories). Then I bumped it up to I think about 1420. And now that I started this program I'm at about 1660 on non-workout days & about 1920 on lifting days. On non-workout days where I still do cardio, I haven't decided for sure but I'm either going to use the 1920 amount as well, OR the 1660 + eat back my calories burned.
I have a spreadsheet I use that has the calories figured out for you per the book. All you have to do is enter your weight, age and height. Message me if you want the link where I got it. I found it on one of the posts in this group actually...