[Hanuman]

There's a lot of tales of this, over the years. I've not had it jam completely, so I don't for sure. However, it was rather difficult to move when it returned from the body shop. Partly, it was the seal itself being sticky.

When you say you've removed part of the seal, does this mean that you were able to get it to tilt? If so, then removing the panel (two pins, one each side) will give you better access to the rest of the mechanism. The sunroof simply slots into the clips at the front, and is held in the frame by the pins. These pins are likely just as stuck through lack of lube and excess of time. So work slowly.
it's at this age, plus a lack of lube, that I'd guess most of the really annoying failures are going to happen.

I can probably scan the pages of the Big Red Book for help once you've got the panel out