Power gains

If you do all of that, you could expect around 35 to 40hp and better take off at the line with the gears. For the money, I would do the gears, exhaust and NOS as a power adder. I've used many CAI's and aside from a cooler sound, I haven't seen any real hp gains from it. Another nice mod to go with the gears would be a stall converter (assuming yours is an automatic). You'll be happy with the performance served up by those changes.

In that case, go with a performance clutch to match the gears. As for cams, not very hard to do just time consuming. Regardless of whether you do this yourself or pay someone, plan on the car being tied up for a few days. Even more advisable would be to do the cams when you have the heads done. Also, with the mileage you have on your car, a 50 shot of NOS shouldn't hurt it, I mean, the car doesn't have mechanical issues does it? If you have a tune shop that is local, do the NOS, install a chip and have it all tuned. With all of those mods you'll surprise the hell out of a few GT's and GM F bodies.