Trek told me their bikes have a 300lbs weight limit. I asked about both full suspension and hard tail. On the Clydesdale MTBR forums, many guys my weight and more use similar bikes. The only time I would worry about weight is the rear rim, since that is all I have had issue with on my Trek 7200.
I don't need to stand to do all climbs. There was one spot in particular with my Trek where I had to stop and get sweat out of my eyes, clean my glasses. It ended up being near the foot of a steep hill and I couldn't get enough momentum sitting to pedal up in in low gear. It really would have been helpful to stand up and rid it, but I was unable to.
29" Wheels and forks do make a difference, but not on a Gary fisher. They are very similar, as all the specs are practically identical. They are designed that way. The guy at the shop recommended me a 24" Trek 4500, and that has the shortest reach of all the bikes, which is still longer than my 7200.