It sounds to me like the free oil change was to get you in to see if they could soak you for high prices for all this other stuff.
Like a previous suggestion, get a second opinion, and don't spend a dime with these guys until you've had some very good references about them.
If a shop is good and reputable in this day and time, they don't need to run free oil change specials to stay buisy.
I would proceed very cautiously.
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in