Whatever you will do (upgrade or dist-upgrade) your system should be working. Most updates we gets from Debian repositories. Only one thing will stop working after upgrading - the marchob-menu we sope about that before.
I did already (for sparky base openbox) and you can replace the depracted marchob-menu for Debian standard menu to get the applcations menu back.
The rest of the system elements and your applications should be working without any problem.
But if you didn't make the upgrade for loooong time it can make some problems. Anyway to make you calm
I made the Debian dist-upgrade on my friend machine after 6 month about and it still works.