Go to Jaycar and get their set. Same thing happened to the set in my old R31 (but Cobra alarm). Costs about $40 back then and hooked up to the (old) alarm without fuss.
Tyres won't cause squeaking. Maybe brake pads, maybe a bunch of suspension related things. Really hard to diagnose over the internet.
Got any mechanical minded mates? Maybe post in your state's section of this forum for help (someone might be able to look at your car)?
Worse comes to worse, take it to a mechanic for a diagnosis.
There are a few 'bolt in' kits available, you're after "return flow" type. Have a browse through some parts sites like Just Jap, RHDJapan/nengun/perfectrun.
Well you car is not "completely stock besides K&N filter" then is it? As above mate, everything you want to know about your car is in these forums, happy hunting! Use google to search this site, e.g. "site:sau.com.au rb20 dyno thread".