I'm with tel004 on a FX 7.2 being a better choice for road use. Shimano's 8 speed stuff is a really good upgrade over a 7 speed as you get a modern cassette and index shifting. I'd feel better with a 36 hole rim but stock bikes in your price range very rarely offer them. At your weight (I was a lot heavier 4 years ago) the rear wheel is beyond normal loads. Basically there are two schools of thought. 1.) Upgrade the wheel and add $150 to cost of bike. 2.) Run original to failure and then replace. I'm in the second group. If you maintain the correct spoke tension the original should last a couple thousand miles. Learning wheel maintenance is a valuable skill to acquire.