'87 4KQ newbie question

[DQVT74A@Prodigy.com ( CHANGLONG HUNG)]

Hi all, 

I am trying to correct the high idle speed at 1800rpm without AC on 
and actually around 1200rpm with.  Recently, a local non-Audi 
mechanic replaced the AC compressor.  Now the car idles high.  I am 
planning to change plug wires, spark plugs and clean ISV and 
hopefully solve the problem.  The new Bosch plugs have 3 prongs and I 
have never seen such plugs.  Do I need to gap them?  If so, how?  
Also, anything I should be careful about besides not to cross the 
wires?  Also, the dash instrument light went out, do I just pull 
apart the dash cover and replace the bulb?  WHere can I get a factory 
manual.  Is Haynes any good?  Lastly, the rear muffler tail pipe 
broke off the other day.  I have called around and Stebro ($640 from 
German Part) life-time warranty sounds very good.  However, I 
recently had the center section(ANSA) replaced under warranty.  
Should I buy the ANSA rear section($159) for now?  Any other brands I 
should consider?  TIA

Sammy