I'm doing a full intake gasket job and decided to do my valve seals and head gaskets at the same time. I had a plan to attack the valve seals while the heads were still on the block, by compressing each cylinder so the valves wouldn't fall through when I took the springs off. When I take the heads off instead, I'll take the valve springs off, and they'll fall out onto my work bench right? Then what do I do? Just slide them back into the head and put the spring and retainer back on? Anything else to it? Thanks.

 

Sorry for the late response, but sometimes the valves stick in the guides after the retainers are removed and won't just fall out of the head. But after removing the retainers, springs and valves, you just remove the old seals and install the new ones.
Since you have the heads off, why not take 'em in and have new guides installed, and maybe a valve job?