I currently have a version 1 jailbreak iphone (bought from eBay...so I have no idea how to jailbreak it again).

It has been working great for months on T-Molbile.

I want to load some applications to it.

Any risks on doing this? Is it as simple as going through itunes/appstore, paying, and loading the apps?

OT1 are the jailbreak phones G3 working fine? I am thinking of buying the same.

OT2 any must have apps?