Hello!
With one machine and a vital work partition it is not wimpy to be cautious!
Before changing Distros and potentially getting into issues with your BIOS (hardware) and GRUB (software) system boot it would be worthwhile understanding why you want to change.
You can test different Distros in LIVE mode without installing them. This can help you understand how well the distro recognises your system.
You can also run a virtual system with Gnome Boxes which is a GREAT way to run another distro, effectively creating a triple boot machine (sort of 
If you just want a different desktop Gnome, Plasma, XFCE … you may be able to install it along side your current desktop environment.
Ideally it would be better to find another old machine to play with and not risk blowing up your essential WINDOWS environment. (Cheap Laptops)
I am interested to see what pops up from your question as it would be great to have a definitive method for swapping out distros on a live system without messing up your BIOS. GRUB can be managed more easily from within your Linux desktop. BIOS management is unique to each manufacturer and often to the model you have. BIOS editing can be very daunting if it gets messed up (in my limited experience).