Should I replace spark plugs when I replace valve cover gasket?
No. You can do the Spark plugs later if you wish. If you want to, of course you can but you don't need to.
Do you need silicone when replacing valve cover gasket?
Although valve cover gaskets don't necessarily need sealers or cements, it's a common practice to glue the gasket to the valve cover. There are a number of sealant choices, too. For this application, Permatex No. 1, RTVs or Permatex High Tack gasket sealant work well.
Should I replace the valve cover or just the gasket?
Valve cover gasket is a simple gasket and needs replacement if valve cover is removed and while changing head gasket which is a major and critical gasket, valve cover gasket is obviously changed. However head gasket needs a change only when blown and coolant is mixing with engine lube oil.
Can you replace just one valve cover gasket?
Yes provided you do not have to dislodge the other in doing so, you are I assume just replacing a leaking gasket/seal that is badly seated, failing, or the cover is distorted due to over tightening, and replacing with a new gasket, if the other is showing no signs of leaking then just replace the problematic one.
Do you need to change oil after valve cover gasket replacement?
What are signs of bad valve cover gasket?
What is the lifespan of a valve cover gasket?
What happens if valve cover gasket is not replaced?
How long should you wait to drive after replacing valve cover gasket?
What does bad valve cover gasket sound like?