As to hotels, check out the Stadthotel Asam located on Josephspitalstrasse. The hotel is located two blocks from the pedestrian zone, and two blocks off of Sonnenstrasse (which wraps around the west side of the city center). Its a great hotel, with all modern amenities and comforts. My family and I stayed there for a week in a 2 bedroom suite in August.

For car rentals, check out sixt - www.sixtusa.com. Sixt has a return location just west of the Hauptbahnhof and I believe there is also one a Stachus (a.k.a. Karlsplatz).