Thanks to everyone for sharing their experiences.... I just had a very interesting conversation with David Poole, who has apparently seen many of these. According to Mr. Poole, there was a point where the construction of the evaporator was changed from epoxy-bonded copper-aluminum seals to welded seals, which apparently are not prone to the leakage with 134a refridgerant. He expects a '97 W140 to contain an evaporator of this welded-type construction. Anyone able to check this on a new (Behr) evap?

I expect to get my hands dirty on occasion with a 10 year old auto... just hoping not to have to do this particular job.

Thanks David!