The best way a sump gasket is done is with the engine out and turned over other wise its very hard to get the sump gasket sitting right from underneath.
Defo... I did my sump gasket about 10 times with and with out sealant / using mirrors to check it / cutting away the sandwich / making studs to screw into the holes to hold the gasket up / using procession torque wrenches etc etc all to make it easier - I never solved my leak - in the end I blew the engine up so sorted then. But good luck anyway
