What involved in a 60,000 mile Maint. and what’s the cost?
I would suggest visiting a Porsche forum and you’ll find out everything.
Call a reputable local European independent mechanic and dealer also for estimates.
First thing - get the manuals for your 911.
What year 911?
The needed items are much different for a 1971 911 vs a 2011 911.
Typical items:
Fuel filter, Brake fluid, serpentine belt, spark plugs, air filter, auto trans fluid.
Everything else on the list are inspections.
BC.
If you don’t have the owner’s manuals, you can probably get PDF versions at the Porsche web site. You might have to register as an owner, but that’s no big deal.
Why don’t you just follow the manual? That’s what it’s for, after all.
I can’t believe you guys expect a Porsche owner to read the manual, what’s wrong with you people? 
I read mine.
Learned some great stuff, including how to turn off my stupid windshield wiper.
If you push the window wiper switch all the way up, it puts it into intermittent mode.
The next notch down is Off.
Followed by Low.
And High.
Pissed me off.
BC.
Gotta love those crazy Germans - that’s the exact same pattern (same switch?) I had in my '79 Scirocco.