You wont need an oil cooler for a 15 minute track session, you need oil cooler if your on a all day track day session. Definitely need oil pressure / temp gauge though
In the blank cover near the rear fog light switch.. The problems were wiring up the horn. Its not easy but then again its not hard if you know what your doing
I have the first boss kit in my SR, horn didn't work and couldn't wire it in so ended up having a button for the horn You could try it but dunno if it would work.. The second boss kit will defiantly work.