I'm almost ready to start replacing the GP's. After cruising the forums I've found a lot of threads about this and reaming is always recommended. I got a set of Beru's for 12.95/pc. and I'd like to do this right the first time, but I don't have a reamer, and in fact I don't really have the time or space to do this procedure properly.

I read somewhere that someone said the GP's could short out immediately if they get carbon on them; is this true? I'm aware now that reaming out the PC can increase the life of the GP's significantly but is it absolutely a necessity if I want to get my car back on the road?

Is there any way by looking at the old glow plugs or any other way to tell how bad the carbonization is inside the prechamber?