SuperG
There's no problem installing Sonar on a new computer - just download the Command Center app and go from there. What you might lose, though, is your project files. Be sure to back them up to another driver, or a USB stick or something.
Your project files are probably the main issue, but if you need to reinstall Sonar, then likely you will need to reinstall Windows, so you are possibly going to lose all your Windows settings, and all your other programs. the settings for those, and any authentication tokens as well. If it is just a piece of bad ram, then you may just be able to keep running the same software system once you have replaced it.
It is certainly worth trying to do a disk image of the system disk, before you let the machine leave your hands. The "local repair shop" can be a place where terrible things happen to your disks and their contents. Unfortunately the problem with the computer is as often as not a problem with the installed software, and restoring an image of a sick system just restores a sick system. If you have software that limits the number of installations you can do, you may be able to recover an installation permission by uninstalling or deauthorizing those while connected to the internet before alterations are made to the machine. And of course if you have sensitive data on the machine, the computer guy will likely have access to it unless you remove or encrypt it.