For inspiration, check out Project Chris Davis. He was, I believe, in excess of 600 pounds, but has now finished dozens of Spartan Races, and has dropped about 300 pounds in the process. Very impressive!!

The Warrior has what I consider to be average difficulty obstacles, in comparison to some of the other races. Remember, you don't have to run between obstacles. Not sure about your course, but if it's on a very hilly spot, you may not be able to run, and walking will expected from many racers.

My real suggestion is to not worry about time. Sure, there's some people who are going to finish in less than 25 minutes. But there's some that will finish in over three hours too. The accomplishment is in finishing to the best of YOUR ability, not beating someone else, in my opinion.

I'd suggest proper gear, no cotton (gets wet and cold, doesn't dry). Go with wicking compression gear. Shoes are important too. I like the Inov-8 Bare Grips, but they are minimalist, and you may prefer a bit more support. But get shoes with traction. There's a bunch that are geared towards OCRs, that wash perfectly clean. I learned the hard way in my first race that you don't want to wear a crummy old pair of shoes that you plan to toss after. No traction!

As far as how to prepare exercise-wise, Spartan Race has a workout that they send daily with exercises geared toward OCRs. It's pretty grueling, but start with one round, and build up to where you can go further.

Trail running/walking on uneven terrain will help as well.

Not really, it just depends on your individual abilities, and if you want to stay together. For most races, I go at my own pace, which is faster than some friends and slower than others. For one race, there was four of us that were pretty much the same pace, and we stayed together and crossed the finish within a minute or two of each other.

For Tough Mudder, it's not timed, and it's a team-building event, so we'll all stay together, even though there will be different abilities there.

Have fun

Outstanding!