Couple gear questions

I currently have 3.23 gears in my 95 z28. From what i've read people with an A4 seem to be going with 3.73 gears. I don't know much about gears yet. I want to wake this thing up a bit. My friend told me not to go dropping a lot of cash on little bs things that barely add power and spend it on gears and a torque converter. Everything on the car is currently stock. I plan to do a few mods to it but nothing crazy. Would 3.73 gears be ok on a stock z28? How would it affect gas milage? Approx. how much time would it drop off the 1/4? And how much should I expect to pay for everything plus installation?

You'd see better results getting a higher stall but you'd get even better results with a stall and the gears.