I've done something similar dozens of times on several EZ's - but not for the same reason as the OP. Most EZ's don't have enough mag to firewall clearance to permit removal/installation of the harness - so...
• mark location of mag case relative to the accessory case with a Sharpie or scribe
• while NOT moving the prop, carefully remove the mag with harness cap intact
• while not moving the mag (or prop), install new gasket and reinstall the mag with the nuts hand tight
• now, you MUST check the mag timing with a synchronizer - you will be close but probably not close enough.
That said, if properly installed, mag gaskets rarely leak. I use DC-4
The RV's I've worked on thankfully offer much better access, so my response is probably moot. Ask any EZ driver if he'd rather change a mag or have a root canal