After a recent update from GOG M&M2 (and my other installed games) will not launch when I select play. I am playing through Dosbox. Does this mean I have to uninstall and re-install and if I do will I have to start from scratch?

Maybe verify/repair will solve the problem.
If not you should copy your game files to another folder before reinstalling, especially the ROSTER.DTA. That's the file where your characters are saved. I'm not sure though if that works, because old games can be "difficult" with their save data.

if it helps i had the same issue when i tried to launch it
after verify/repairing it worked fine

Thanks man, the game works as intended. Cheers!