1997 Toyota Camry Oil leaks

It seems like oil is leaking from around the seals above the oil pan. Econo Lube had changed th drain plug, and it stopped for a long time. But recently it just started leaking again, and it's hard to tell exactly where it's coming from. The local dealership and other shops have proven untrustworthy when it comes to troubleshooting. Exorbitant costs, that don't always solve problem.

I've put engine stopleak in about 1500 mi. & 1 1/2 qts of oil ago, and was told by Auto Zone, that it was ok to put more in now. But a friend said that would cause seals to expand and cause more major problems.

Where should I start first? & How can I be sure repairmen are correctly determining the problem/ solving it? Any referral to a reliable toyota repair shop in Mission Viejo/Lake Forest Ca. 92691 area?
Thanks.