Me and my mate go to the gym often now, been going for nearly 2 months now, 3 times a week and you can see and feel the difference! Just ask the gym/fitness guy who runs the place to help you out, explain what you want and he shall show you what exercise machines and weights you need to do to build your upper body :- (N)
I really enjoy working out, and it also make your bike feel lighter etc... :)
Have fun :-