I can't speak to the questions in your post, but to answer the question in your post title, "what do you need to know", you should know that rear projection is on its way out. The companies making them are scaling back the production of RP big time. You could buy an RP, and then be stuck when there are no bulbs to buy someday! And this is from a cat who owns an RP!
Being purely selfish, I hope you buy RP anyway, cos if enough people do, maybe it'll convince the big companies that people are buying them anyway! I'm sure others here can comment on that specific model. Good luck with your buying decision!
cheers,
supervij