Mercedes Newbie with questions

[Shocker]

Hello.

I have a few questions about a 1999 SL500 that I am working on.

I am a custom bike/car shop owner, but have never worked on a MB before. I have a very good customer who wants a few things done to his car.

1. A 50,000 mile service, ie air filter, plugs, plug wires.

2. A problem with the A/C.

So, here are my questions. What does a 50,000 mile service entail ?

Will I need any unusual or special tools?

The A/C is presenting the following symptoms: When the car is started, the A/C blows cold and everything is fine. Once the can reaches normal operating temp. it just stops blowing cold. The fan runs fine, but only warm air comes out, rather than cold. Is this caused by a bad compressor, the cabin thermomenter, or???

Thank you. I greatly appreciate any help anyone might have to offer.