Make sure you've got ALL the bolts - they sometimes hide on you...
After you've got them out, I find fetching it a nice whack on the side with my 2# rubber hammer usually works well. If I think it's the original seal, I'll whack it three times on top good and hard (one at the front, one at the middle, one at the back) to break the seal and then fetch it a nice whack on the front/side - that usually does it.
I'm a little leery about prying on the mating surfaces - it's usually a "weapon of last resort" for me...
5-90