you don't necessarly need a wideband gauge. most times the dyno you'll go to will have one and once your tuned you should be ok. but if you wanted to save money on a dyno and buy a wideband gauge then street tune it, thats not too bad of a deal either.

the type of tuning you'll be doing isn't too bad. since you have a header you'll more than likely need to add fuel in the upper rev's. you could datalog your air fuel with the aem then add fuel where it starts going lean on the maps and once your happy with that you can retard 1 degree of timing from the nitrous activation point to redline(i'd keep it around 3500 rpms) and go do a nitrous 3rd gear pull(keep in mind bottle pressure its safer to tune with high pressure like 1000-1100) then you know if the pressure is lower you'll still have plenty of fuel. then just keep hawk eyes on the air fuel gauge(and the road of course) if you see it start creeping into the 12's or higher let off and go one size larger on the fuel jet. if it goes into the 9's(which it most likely will. lol) you can go one size smaller on the fuel jet or just keep it like that for super safety. high 10's to mid 11's on the spray is the optimal zone to be for safety and power (on pump gas). low 13's to 13.3 is optimal for naturally asperated engine at WOT(off the bottle).

once you get your afr's on the spray where you like them. you can do one final safety check. throw in a new set of plugs and do a 3rd gear pull to say 6500(on a closed road or race track ) then at 6500 shut the car off(turn the key off) and safely pull off the side of the road and pull out your spark plugs and "read" them. what you'll be looking for are little speckels if you see them then you need to retard more timing.(because thats part of your piston) the plug will most likely have a blueish hue on the ground strap because of the nitrous, this is normal as long as its not dark blue. you'll want to make sure the plug is not super white on the insulator it should be a little white with maybe a light browning. another thing to look at is the discoloration of the base of the plug(where the threads start) the discoloration should not go past the second thread if it does then you will need to go one more step colder. another check which is a little harder to see is the ground strap will have a slight discoloration as it travels to the base of the plug. the discoloration should be right at the crest of the bend. if its closer to the electrode then you could use more timing, if its closer to the base of the plug then you'll need to retard the timing more.

I hope I didn't confuse you. you really don't need to do the plug deal unless you want that added margin of safety or want to maximize the setup. honestly a 50shot is very safe and most times you can just slap it on and go. but I figured your somewhat concerned so here are just a few pointers I can give from previous experience. to me tuning is half the fun. i've gone from a super rich untuned 75shot to a tuned 50shot in the past and the 50shot was faster. which means more fun per bottle.