cheap/easy way to swap valve springs at home
Place heads on a smooth surface, A piece of plywood is nice.
Use a large enough socket 3/4-7/8 to fit on outer diameter of retainer. Nut opening down, smack socket with a 2-3lb sledge pretty briskly. Lock should pop out and retainer comes loose.
The multi-groove locks can be a pain to remove.
That's how I do it most of the time.
Putting them on, you'll need a spring compressor.