is it ok to upgrade to a used T4 from the stock gs-t's turbo, forget what its called but a t24?

you will need other supporting mods.

your stock turbo is a T-25 if you have a 2G....the 1G has a 14b.

Other supporting mods would be what exactly? cat back w/ headers? stuff like that?

injectors and some type of electronic fuel management unit