If what you go into service for had a basis on programming, they will reprogram the car and restore things to default, so any customization will be lost. But, a generic service call does not usually require reprogramming and BMW does not, generically, update their vehicles to the latest version unless there's some defect affecting the owner and reported, or there's a safety issue. IOW, taking the car in for service does not mean it will automatically get the latest software.
FWIW, much of what you are talking about in coding is easily done with the BImmercode app, which would be much simpler to do yourself versus driving it somewhere to have someone else do it for you. This assumes you have either an Android or iOS phone or tablet. The software license isn't much, nor is the adapter needed to pair it to the car.
2011 535i x-drive GT, 2014 i3 BEV