C230 A/c Recharge

[JTWII]

A/C went warm on my '98 c230 last night. I want to simply buy the refrigerant (R-134A ?)at a local auto parts store and recharge the system. I will probably have the complete A/C service done next Spring (drain....replace oil...recharge). I have a few questions:

1. Am I going to do any harm to the system by simply filling it up again with refrigerant ?
2. Is this a simple procedure I can do in 10 min ?
3. Where is the receptacle that accepts the refrigerant in my engine bay ?

The car is only 3 years old with 35k miles, I do not think anything is wrong with the a/c system, it just needs refrigerant.

Thanks.