I bought a 2011 G37S coupe in March with 44,000 miles and a year with
the basic warranty still in effect. My question is I have a carfax and the
dealer's (Pacific Nissan) in San Diego prep fee that itemized the required
regular maintenance for the mileage, but since it a used car, what type
of proof do I need to enforce warranty with the Infiniti dealer?

 

Nothing unless the dealer asks. Most items that come up require little to no paperwork on your end. I suppose if you had an engine seizure they might ask for maintenance records, but you should be OK otherwise. If the car has been serviced at a dealer any other dealer will be able to pull up service records.

 

You will be cover until 5 years of the original in service date or 60k miles, which ever comes 1st your 100% covered.

As long as the car is in stock form (engine no tune / intake or exhaust) you will not have any warranty problems with Infiniti.

Did the dealer you bought it from give you any service records ?
If not contact Infiniti corporate give the vin, they should be able to tell you what dealer the car was originally sold to.

I did that on a used Audi a4 Quattro.
Was a 5k car with 110k on it, I contacted Audi USA & found the original dealer in Connecticut. I bought the car In NY, so I wasn't taking any chances.

Was able to find out what was & what was not done.
After getting that, I then negotiated both price & parts to be either serviced or replaced.
Good luck with your new ride,btw.