Service questions: Keylless/Light/Motor

Have a few questions before I make the big trip to: Fresh: Keyless Go door lock defective, on all doors search function means that if a door is defective, everyone can be disturbed. Backlight half of the trunk lid had a suspension. In addition, it always switches off when the tailgate is opened or closed, of course the headlights are on. (a wanted funk sound?!) Search did not help. Standlight defective. What costs actually such a Change? The search function has shown that you could do something like that yourself, but I’m not exactly wild about disassemblying my car. What older: decorative strip of the window top partly from the anchoring. What does such a thing cost? And last but not least: when I wanted to start the cold engine (V8) today he immediately switched off again, only electronics remained on. This has happened in the past already the more open, maybe once a month or even less but now immediately two times a day. l in one day (each cold engine). In addition, when changing from the 1st to the 2nd gear and back it is easy. In addition, an oil change should be due (LongLife) but the car has not yet reported. Ok, thank you for reading and for every tip/ advice etc. until then