I've got an oil leak underneath my 90 GTC-VNT, and it looks like it's coming from behind/above the oil pan area, and likely the transmission, as the areas above/backside of the block/turbo are dry. It's sat for probably the last 10 years with little use. Are there potential areas that have been typical trouble spots for transmission leaks in that area? It's not coming out of the crankcase/oil pan area, as the oil there is still full. If so, is it typically a relatively inexpensive fix with seals and such and are they still available? And once I have it repaired, I'd like to upgrade the lubricant within the trans, it's typically been 10-30 engine oil, is that correct? Any knowledgeable help would be most welcome, thank you.