When you say the corrector has moved I assume you mean the baffle that is stuck to the shiny spot. That part is pretty easy to fix, and if you do a search for "ETX 90 baffle fix" you should find some directions. My advice is that when epoxying the baffle back into place use incredibly tiny drops on the baffle. Otherwise you end up like me (and I thoughjt my drops *were* small!) and having glue ooze out from under the thing all over the mirror spot and panicking and frantically trying to pull the baffle back off and cleaning up the epoxy with alcohol before it sets and ruins your mirror. Mercifully it all cleaned up and no harm seems to have been done to the mirror spot, or at least not enough that I can tell any difference using the scope.
Repairing the drive is beyond me, I'm afraid. Fortunately, it's not hard to de-fork the scope and use it on a conventional EQ mount, so that's always one back up option if you want to keep the lovable little scope.