I bought a '00 E320. Questions about : Tranny fluid, engine oil, & harmonic balancer

[The Godfather]

Howdy Dr. ///AMG in da house with a new car coming next week (or maybe the week after next...mmm sounds like the movie friday.. ok ok enough!!!) and well I don't know much about the new benzo's, since in my family we've only owned W124's (wagons and sedans) and a W201.

So with the arrival of the '00 W210 320, come questions:

1. Do you recommend doing the tranny service, although they say it's a lifetime fill ?
How much will the tranny service be ?

2. Engine oil: Always use mobil one synthetic, or is it ok to use regular oil?

3. What's the harmonic balancer? What does it do? I was told by Mark Cummins that they are prone to go bad and could cause severe troubles. Do I replace it? Do I check it? Can I check it?

4. Should I take my car to the stealership for the initial check up, or take it to an indy shop. I'm thinking stealership since there's a lot of electronic involved, that an indy may not be acquinted with.

So thanks in advance for the answer

Oh and here's a pic for you guys to enjoy The car was purchased on eBay and it coming from TX to Cali. btw it has 67k miles.