One of the most important mechanical parts in the engine!
If the inlet or exhaust valves are damaged, bent, or pitted, the performance will be down, with loss of compression, poor gas flow and unpleasant mechanical noise.
During an engine rebuild, it is a better option to renew the old, worn and brittle valves, rather than trying to penny pinch and compromise the reliability and long term durability of your engine.
Renewing the valve springs and these retainers and seats at the same time is vital to ensure those new valves don't float at high revs destroying themselves and the piston!
You may wish to consider:
Why not order all the gaskets you require at the same time - save money on shipping costs with a multiple order. Try this gasket sealant: 08C70K0234M as used by workshop professionals.