Take care of your fluids, maintenance items, any leaks, then replace your broken pieces in the interior, and the dents on the car (go to a dealership and get a PDR 'paintless dent removal' to do them for cash, shouldn't be much), before worrying about upgrading your headlights, tails, and signals. However, you may want to replace the tail lights first, because the rear brakes not coming on are most likely due to corroded circuit boards in the stock tails, many of us have upgraded to aftermarket LED taillights to bypass this known problem.

Powdercoat your rims if you want to do it right, usually costs about 100-150 per wheel, you have nice 87's do them right, they are chrome now but they are among the most desirable wheel design for the E53! What stock wheels did you put on instead?

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2018 Ram 2500 6.7L Cummins 68RFE
19k miles -Bright White/Black - Big Horn Sport - Crew Cab Short Bed
2013 X5 35D (CEO's) - Born on 5/17/2013 -
82k miles - Alpine White/Cinnamon Brown/Premium Pkg, Sport Activity/Premium Pkg and Sound/20" Style 214/Running Boards