Toyota Repair: Toyota problem is driving me crazy!, pan gasket, toyota camry

Question
I have a mint cond. 1996 Toyota Camry 4 cylinder with only 85k. Suddenly developed moderate oil leak. I have had 3 mechanics look at the car a total of 8 times. Had distributor o-ring, pcv valve, and finally, oil pan gasket replaced, the last repair done twice. Still it leaks! Dye put in oil twice. Mechanics say it seems to be a rear oil seal leak, but they are not sure, but they also say these particular car models don't suffer from this kind of problem. This is a BIG repair, requiring trans removal, so we are being cautious about it.
Is there a definitive way to determine this leak? Are there any sure symptoms of a rear seal leak? Can additives help?

Answer
I think that there may be a problem with the oil pan leaking still, the rear surface of the oil pan must be covered with sealer all the way across or it will leak, I have seen this happen before and if the sealant(there is no gasket) was not applied correctly there will be a leak that may appear to be a rear main seal leak.
Have someone that knows what they are doing check for this, try the toyota dealer, I don't think the rear main seal is leaking either at this mileage.