2003 Mercedes S430 Battery is Dead and Can't Unlock Trunk With Key

I called MB roadside assistance. They told me to spray WD40 into keyhole near trunk to get out the gunk, then press on the gray clicker 20-30 times. In fact, she said that's exactly what roadside service would do. I had seen a YouTube video with someone showing how you can hack up the car and connect positive terminal to alternator and negative to ground. When I mentioned this to roadside customer, she said she wouldn't recommend it because it could burn out some computer settings/read outs. She said that I would need to have the car towed to MB service who could hook up the car to dome computer that can unlock the car. Sounds like that could be expensive but I don't really know yet. What are my options? And why would connecting jumper o alternator cause damage? Would doing this allow me to use my key fab to open the doors? Any guidance you can provide would be greatly appreciated.

DJ in Houston