Upgrades for 97 V6 Vert

CAI, exhaust and pullies are easy bolt ons and will help future mods you're doing to the car.
Not sure ho much you're spending, but getting ported heads, intake and a bigger cam can net you up to 100 extra hp.

If you're going gears, just get a GT (8.8") rear end with the gears already installed since it's cheaper and stronger than the stock 7.5"
Doing just the gears in a stock rear end and not a T-lock is waste of money (in my mind).

Figure out what route you want to go, then after those are installed, get a programmer (or at the same time)