Yep, time to split the cases, but, don't do it upside down. After you have everything ready to split, with the crank gears removed, put a ratchet strap from 1 end of the crank, over the head, between the spark plugs to the other end of the crank. Just tighten it snug. Don't get carried away. Then lift the top case off, leaving the trans in the lower half. While it's apart, flip the top half over, remove the ratchet strap, lift the crank slightly and replace the crank seals. Check to see if the crank pins are welded. If they're not, do a complete teardown and send the crank to be trued and welded. If it's a stock crank and it is already welded, make sure the pins in the crank bearings are located properly when you put it back together. Also, make sure you remove the steel strap behind the clutch basket that ties the top and bottom case halves together.