Key fob died on my E-Class, anyone know a good auto locksmith near MBZ?

So my key fob just completely gave up on me yesterday, wouldn't even unlock the doors and the dash kept saying key not detected. I panicked a bit because the dealer quoted me something insane for a replacement and said I'd need to tow the car in. A mate told me to look for expert remote key coding and ECU programming near MBZ City instead of going straight to the dealership, said there are proper specialists around who handle this stuff without the drama. I found a place online that does car key programming in Abu Dhabi and they reckon they can come to me and sort it on the spot. Has anyone actually used a mobile service like this for a Mercedes? I'm a bit nervous about someone messing with the ECU on my car but the dealer price is just not happening right now. Would love to hear if it worked out for anyone or if I should just bite the bullet and pay the dealer.