Can I include self-employed vehicle expense deductions - model & year, new or used, annual miles, work miles - when I have already deducted work mileage at the IRS rate?

What do you mean you already deducted work mileage?  For your W-2 job or for your self-employed work?  You cannot deduct miles for your W-2 job.

If you deducted mileage for your self-employed work, you can enter your actual expenses, however, TurboTax will determine which one gives you the better deduction.  You cannot claim both in any one year.