I just bought a gorgeous 1986 300E, but... the air conditioning pumps out room temperature air. Assuming it's not a thermostat problem, am I doomed to having the AC unit replaced or is there still a legal fluid I can recharge it with?

Sure, it's still legal to recharge an R12 system, it just has to be checked over for leaks, so it's not as simple as it used to be. Considering the cost, it doesn't pay to put it in and not check for leaks anyways.
Gilly

Thanks! That's a relief.

Check out http://www.id-usa.com

I just did my '81 and it blows COLD air.

TOO cold? Or are you saying it's working normally?

Hey man,
I just took my 1983 300D in because its blowing less than cold air when i took it to Boston yesterday, and providing it has no leaks they will charge me $142, for 1lb. R-12.
Since the air it blows is slightly colder than the economy setting, it must still have some in it and shouldnt have a leak. What prices are you guys facing?

When I bought my 300E in October of 98, I never really tried to run the A/C much (stupid move). It was cool anyway, but as it warmed up in the spring, realized that there was a leak, since I was getting warm air too.

Dealership diagnosed that the evaporator needed to be replaced. That requires the removal of the dash and an expensive unit which totaled $1800 (I guess the previous owner found that out too and cut his losses). Fortunately, I had purchased an extended warranty, so I was out the $250 deductible instead.

I had a really nice Jag convertible that also had the evaporator go out the following year. Quoted about $3000 for its replacement including labor, so I cut my losses and traded it in for the 500SL we now have.