Hi John,
Our 2011 Rushmore has auto-hydraulic-leveling with individual jack control as well as individual slide controls. If the hydraulic pump fails to operate under electric power, it's possible to turn it with a drill while opening/closing the individual valve controls as needed. This procedure is described (at a high level) in your manual. Figuring out which valve does what is the hard part. Slide control valves are on the pump assembly and on our rig landing jack valves are on the landing jack posts. But I'm told that varies quite a bit.
If by "blown seal" you mean that hydraulic fluid is spurting out when you try to move the slide, and there's not enough pressure to operate the slide, I don't believe there's any override for that. You'll need onsite service. If you mean that it's leaking fluid but still operates, I'd get to a service location soon, before you get stranded.
We had a hydraulic fluid leak from the pump last summer. It was enough to make quite a mess, but by adding fluid a few times I was able to nurse it along and continue our trip. I was taking a chance that if it got worse, we might need onsite service. It probably leaked 16-24 oz of fluid at each campground (setting up and then packing up). An o-ring on the pump was the cause of the leak.