They can be difficult to pop loose, the only other thing is to remember to get the sealing washer in the right spot when you put it back together.
You can replace the gasket, or use a form-a-gasket product instead.
While you have the cover off, it's a good idea to check the starter clutch bolt. They are famous for being undertorqued and/or missing Locktite. If you don't have a service manual, you can d/l one in the Members Section of the board.