how do you make sure each piston is at TDC when the cams are out? because without the cams in, you can't line up the dots on the cam gears since you have to take out the gears, correct? so what are you doing? putting a long screwdriver down the spark plug hole?

 

TDC is marked on the crank... so that is cylinder no. 1. Then turn it accordingly for each cylinder is my guess. you could take a flashlight and look without taking a screw driver and hitting your piston with it.

 

Could someone post pics of damaged or failed retainers after they have been removed from the head? It would be beneficial to examine the actual part.

 

I don't think it is absolutely necessary to have precisely TDC when doing this job. You only want the piston at or pretty close to being at the top so that if, for some reason, the valve lets go, you can easily fish it out and it doesn't fall too deep into the cylinder. If you see it come up as far as it can through the spark plug hole, lock the piston there and that should be good enough.