Someone just gave me a nice old RIH Bustraan bike, with a broken rear derailer, and I want to convert it to a fixed-gear.

Not having much mechanical experience, I'm looking for somewhere/somebody in Amsterdam who can help me get the thing fixed up. I'm from Seattle, where the streets are crawling with fixies, but they are rare here and the shop guys I've talked to don't seem to be into this kind of thing.

Any advice?