'02 300M: A/C doesn't, hissing sound, oily smell

Our '02 300M's A/C seemed to be incapable of producing really cold air.
Then, while my wife was driving it, she said she heard a hissing noise,
and now I detect an oily smell. Seems to me like an evaporator failure
(which I understand was a common problem).

How easy is it to fix this myself? The books and Web sites say to have
the refrigerant recovered professionally first, but I'm guessing that
there's none left anyway.

I saw estimates of $1000+ from a few years ago, but an after-market
evaporator is only $100, a receiver/drier $27, and replacement R134a not
a whole lot.

Somebody reported that the problem on his was merely the Schrader valve.
Where is that located?

Perce

 

The Schrader valves are in the service ports.

It isn't just the parts either. You also need the tools, such as:

Vacuum pump (preferably 2 stage) with new oil.
Micron gauge
Digital weight scale
Manifold gauge set
Several accurate thermometers of various types.

The vacuum pump removes all air, moisture, and other contaminants from the
system leaving just the oil.

The micron gauge lets you know when a deep enough vacuum has been reached
and when all the moisture has been boiled off.

The weight scale lets you weigh in the new charge of 134a.

The gauge set connects the vacuum pump and charging cylinder to the system.

The thermometers working along with the gauge set can tell you the vent
temps and line temps so you can check for proper operation of the system
such as the suction line superheat and liquid line subcooling.

Then of course you need the knowledge to understand all of that and put it
to good use.

 

Aren't the fancy tools and other equipment just for recharging the
system to the correct level? If so, couldn't I do everything else myself
and just take it somewhere to have it recharged?

Perce

 

Yes, but whoever does it needs to pull a good deep long vacuum or you will
have problems later.

 

Yes you could and might be an excellent middle ground.