I drive alot in mine every week 04 ssb 6 speed, I keep xtra sensors in a box in the back, but 98k miles and have not had to change one yet.
Not many options for additional power.
Eurocharged tune.
Cai, cold air induction.
Throttle body.
Exhaust.
Pretty much all that can be done on a mercedes.
I have the 558bt head unit (silver) with the pyle plp 6.5 upgrade behind seat, sounds alot better than stock in my opinion.
I use the cupholder that slides down between the console and passenger seat, works good, and a small bin in passenger seat.
I drive 2-6 hours twice a week.