A Service Question

HI... i'know the A/B Service has been covered many times but i dont' really have a definitive answer. I'm out of warranty and I'm in need of an A service for my 02 s500 85k. Looks like i need an oil change and a little lube and tire rotation along with checking a few things that any lube shop would check.

Dealer wants $350 - indi wants $160 - Mobil1 Lube Express $115 - Tire kingdom $66 (synthetic just not mobil1) I'm sure the tech at Mobil1 or tire kingdom is not that experienced with MB (although in my area there are lots of them) butoil change isn't not that difficult... or is it? I will be getting tires soon so the rotation is no biggie, any words of wisdom are appreciated.

thanks
wes