I don't have all the answers but I'll try - hopefully a couple others will join in.
1) As best I can see the fan is controlled by a circuit in the power supply unit - which in turn is triggered by the controller. It seems to be linked to the safelight control circuit as well. I haven't figured out if there is a separate control signal for the fan or just one from the controller to signal the safelight and the fan. There is a timer circuit in the power supply which keeps the fan on for time (2-3 minutes I think).
Now two questions for you. Do you have a safelight hooked up to the power supply and is it going on and off as expected? Does the power supply - head connector have a round pin or are they all flat?
2) I have no idea who could fix them. Sourcing a new fan motor might be fun. I think most of the chips & transistors are still available but not 100% sure on that. I too have a second system as a "spare" just in case.