I really want to make it a mild street machine so I thought cold air intake was #1 on the list...now I am second guessing...
I'd say more like last on the list, and even then only if you've done other significant performance mods to require more air. FYI, Volant is the only manufacturer who makes a sealed intake system for these trucks. If you absolutely have to have an aftermarket intake, I'd get one of those. The stock Vortec intakes are better than any of the other options on the market IMO.
Quick tip for the stock Vortec intakes though... There are two different size filters that fit in the box. A standard, and a larger "high capacity" filter that the K47 optioned trucks got. Make sure yours has the larger size next time you change it. I use ACDelco part number A1301C in my '97s. Note that none of this applies to the diesel trucks, their K47 "high capacity" intake option is an entirely different deal with a different box.
If you want better performance, I would spend money on exhaust and a PCM tune first.