At work, we have computers in industrial cabinets, with their own forced air systems, and the problem we have is with dust getting into them. Even with filters the insides have to be cleaned quarterly. I can only imagine that in a workshop with a lot of sawdust this will be an even bigger challenge to keep the dirt out.
That said, if you could build an airtight box (with a window for the monitor) to keep the CPU and monitor in that has adequate filters and fans to keep them cool and clean, and just leave the keyboard and mouse exposed to the "elements" you probably would be OK. Keyboards and mice are cheap enough now that if you had to replace them each year it wouldn't be more than $25.
As always, surge protector, etc, and don't leave it running when not working in shop would probably be good safety practice.
Or, if you have REALLY, REALLY good dust collection, you could hope for the best and just set it on your bench...........
Just a humble opinion,