how to install a tach and misc??

i have a 2000 mazda b2500 4 cylindar 2.5 L and i need instructions on installing a tach. also i was wondering if anyone knew any good sites to put aftermarket parts from(body kit, engine, etc.) and about how much hp and tourque does it help. anyother info about my truck and ideas on hooking it up would be nice

Thankz_