http://intense-racing.com/Merchant2/...y_Code=3800_PP

I'm thinking bout getting this after awhile and was wondering which plugs, T-Stat, oil filter, and accessory belt I should get for the best performance. Right now my engine is still entirely stock. The extra $18, $5, and $4 dont matter, just looking for the most HP/acceleration gain I can get with this package. How much HP am I looking at gaining, if any at all? Also, it says its for a Series II or III and I have the Series I, is that gonna be a problem?

You are best piecing that tuneup kit together yourself. That kit is for a Series II car and will not work on a stock 1994 engine, supercharged or not.
The plugs, wires, t-stat, t-stat 0-ring, fuel filter, and oil filter will work, but the accessory belt is different.
I suggest you get:

Napa Belden Max 8mm wires
Autolite 605 plugs (gap at .057" if you have exhaust work and a custom intake)
180* t-stat
T-stat gasket/o-ring
Fuel Filter (just get a NAPA gold if they have one when you pick up the plugs, wires, etc..)
NAPA GOLD filter (just make sure you get a WIX filter for a 4.3L Blazer -they fit right on and have more filtering capacity)
For the accessory belt get a Goodyear Gatorback.
Same for the SC belt if you are changing that.

I hope you dont think im questioning you, Im just verifying for my own knowledge.
Only 1 heat range cooler plugs? I was told to go with at least autolite 104'*, what would happen if I went with cooler plugs than the 605? Wouldnt the 160 T-stat be more effective? How much you think this will run me and how little gain will I get from this?

The 160 will do you no good at all. In your climate, in addition to not having the programming to properly support the 160, the 180 would be the better choice.

In fact, the 160, without supporting mods for it, will be way more detrimental than even a stock stat. Fan on/off times need to be adjusted, open/closed loop operation will also need to be adjusted via programming if you go the 160 route.

Aight, 180 it is. What about the Autolites tho?