Congrats! I'm not far behind you. I will be making my last payment on my '07 4R next month, which is a year and a half earlier than the initial term of the loan.
Other than routine maintenance, I would just make sure you keep your car clean this time of year. Looks like you reside in the northeast, and I know they are not shy about using a lot of salt on the roads in you neck of the woods. Rust can be your worst enemy, especially if you plan on hanging onto your 4Runner for a while.