I find if you run the motor first so it's warm you should be able hit the cover off easily with a bit of wood and hammer or big screw driver and hammer.
If it has a gasket that rips and you clean the surfaces with petrol or thinners but leave the old gasket in ,silastic high temp will seal the gasket back together.
I have high temp silastic but if I didn't I'd just cut a new gasket from gasket paper if the old one was damaged.
Gasket Paper 1.5mm Thick S-207 150mm x 150mm Sheet is about $10. with free post or you may get silastic cheaper.
If you don't have wad punches it's probably easier to get a VALVE COVER GASKET FOR a HONDA GXV160 for $10 with free post when not using silastic.
A couple youtube clips to remove the cover but I haven't had a look at them.
If the cover gasket doesn't get damaged when removing the cover I'd just put it back on.
