hi i've had a 2001 base auto maxima for the past few years. been reliable and want to invest some money into it to keep it lasting forever.

23 years and 120k of nyc city miles but was garage kept most its life and rust free.

any preventative tips?

have recently done:
fluids
front right wheel bearing
tints
muffler
aux
wipers
etc


looking to upgrade and looking for suggestions:
suspension (shocks and springs)
wheels n tires
interior lighting and interior
carplay head unit


and of course the car has some issues:

just had the main engine belt changed thinking it would fix a whine under heavy acceleration and it didn't. anyone know why this might be? maybe exhaust like the cat?

upgraded to the hid headlights from ebay that are in the 02/03s. don't know what to do with the extra wiring do i need a cable converter?anyone know where to get it?

basically i need all the help i can get