Case 530 LP Draft-o-matic Problems

I have a 1967 Case 530 LP Draft-o-matic row crop. Here is the problem. The tractor leaks oil around the oil pan back into the clutch housing and it drips out on the bottom of the tractor around the power steering cylinders. The local Case IH place has tired multiple types of oil seals to try to get the leak stopped. Nothing seems to work. It only leaks after the oil gets hot. I had a new clucth put in the tractor at the Case IH place. Can anyone help with solutions to the problem of the oil leak? This is the only oil leak on the entire tractor. I even checked the block for cracks and none were evident. Any suggestions? This will be the 5th time the Case IH place will have tired to solve this problem. I also have a question regarding checking the hydrolic fluid on the sticks at the seat and at the front tank. Should you check the oil with the stick screwed down or not screwed down? Thanks for all you help.