Time for a new Batmobile?

I have a 1999 Nissan Altima with 175K miles on it. I drive 500 miles per week and have been doing so for the past four years, so many of these are highway miles. My mechanic is advising me to flush the transmission, put on new belts, get it aligned, and replace a tie rod (all totally $500-ish). My car also has a broken windshield, cracked taillight, and just recently I took off the driver’s side rearview mirror backing out of my garage (whoops!). It also has a short in the turn signal which makes it click on and off randomly. The car is paid off. Is it time to get a new car or would you put the money into the car to get some of this fixed? The missing mirror really bothers me.

Thanks for your opinions!

Renee Batman (yep, it’s Batman!)