I was told by another forum member here that this could be done without taking the heads off of the car. I have the valve covers off...can anybody tell me how I'm supposed to break the valve stem retainers loose from some grimy old springs?

First you'll need to figure out how you're going to secure the valves to ensure they don't fall into the cylinders. Some guys use compressed air (via the spark plug hole) to hold them in place. Some guys just bring the piston on that cylinder up to TDC. I've also see magnets that can hold valves up. Second you'll need a valve spring compressor. There's a couple different styles depending on how you want to work. Check Jegs or whatever.

Once you compress the spring the keepers will easily slip out of the retainers. Just watch you don't drop them in the engine. Good luck.

Therein lies the problem. I can compress the spring just fine but I cant get the end of the stem and the keepers unjammed. I'm going to try that compressed air idea but i doubt it will work better than a pair of pliers. Frustration!

Before you compress the spring hit the top of the valve with a brass or plastic hammer a few times. That should break it all loose. Then compress the spring and pull the keepers & retainer off.

i take the plugs out and fill the cylinder with rope...

to break the retainers and lock free i use a short socket on top of the retainer and a rubber mallet give it a couple of wacks make sure you are hitting square to the valve you will feel the retainer pop off the locks then you can compress the valve springs and i generally use a magnetic to pull the locks out

yep i agree