canon IIIa -- erratic slow speeds

This camera just arrived yesterday and the first thing I noticed -- I always test shutter speeds first and slow shutter speeds at that -- was that the slow speeds are erratic. Once I take the camera off the slow dial, though, the speeds sound about right -- at least 1/40 - 1/100 do.

I've worked on cameras and lenses before, never one of these things, though. And I'm wondering if this is something a person with a reasonable skill level and a decent assortment of tools can do -- or will it require a pro with specialized equipment?

The camera is in very clean cosmetic condition -- I don't think it was ever used much -- so I'm wondering if it might just be a simple lube issue.

Most likely it's as you think, cleaning and relube.

As fortune would have it, I did a bit of searching on the subject and came across a couple of tech note pages by Rick Oleson on the topic of repair and maintenance of the Leica rangefinders. And since this Canon is such a close copy, I'll be able to use his notes. It should get me started, at least. Here's what I found:

http://rick_oleson.tripod.com/index-155.html
http://rick_oleson.tripod.com/index-154.html

Rick's tech notes have saved my bacon more than once. I should always keep him in mind when I have a repair question. May good health and fortune shine upon Rick always.