If it's just for a simple service, any mechanic can do it, there's nothing overly complicated about the 350 thankfully. I would probably buy all my own products though and make note of the oil capacity to save them having to search for the info and possibly getting it wrong.
As for the tyres, the OEM Bridgestone Potenza RE040's are pretty awful, so if thats what you're still on I'd be changing to something else like Michelin Pilot Super Sports or Michelin Pilot Sport 4S.