Thanks for all of your help! I may be able to get away with only replacing the passenger-side mount for now, but I'll probably end up doing them both while I'm down there. I'll definitely use some wood to brace the oil pan, and I'll check to make sure everything is clear before I brace the motor with my floor jack.
I'm looking forward to seeing how the car behaves with the new engine mounts -- I've been hearing a lurching noise for some time now, and I think this may fix it. I had thought it was from the struts, but they were replaced a few months ago and the noise persists... I'm hearing it more often now that one of the mounts gave out.
Again, thanks for all of the advice. I'll post again once I'm finished to let you know how it worked out.
1988 Mercedes-Benz 300E
2008 Honda Pilot