An update for anyone that's interested. Been ticking a few boxes off on the E39. Alot of the work that needed doing, just needed time and some fiddling. Headlights polished and ended up being the retrofitted Hella kind. The sunroof drains were loose, letting the water in through the a-pillars. A bit of RTV and some weed-wacker-wire to clear the drain and it's good as gold. New number plates ordered to replace the beat up ones, a $23.50 bargain. Got a new front guard from pick-a-part. Rear cup holders and vent replaced. Rear window regulator replaced (swaged portion on the cable had come out of bracket). Leather cleaned and looks great. Found and fitted a rear cargo cover and net. New tailgate liner (still need to fix locking issue). Wheels cleaned up quite nicely. The oil burning and dropped cylinder ended up being a tired CCV. Replaced it and it runs mint. Has a new radiator, thermostat and water pump. Just going to replace the hoses and the expansion tank. Money saved from not having to swap the engine will go to the roof repair. All in all, happy ish with the car once I got over the initial shock. Realising now how hard a black car is to keep clean lol.