or is it as risky as buying a used car?

its risky...but every now and then my famliy's auto garage has to go find parts that arnt made anymore at a parts yard... if you need to, go to one that has a good reputation and if its a serious part have a machanic check out the part. but still there are never any garantees

Most good parts yards are set up online to sell to repair shops. You can also use these sites to search for parts. As with anything used, you need to be careful and know what you are looking for.

See here: http://www.used-car-parts-exchange.com/

and here: http://www.urgpartsearch.com/link/search.cfm

and here: http://www.car-part.com/

I love junkyards... I found one near me that has hundreds of cars, so I'll just take a toolbox and a bunch of tools, and go and check it out... If I know what I'm looking for, I'll find it and take it off... just try to find a newer car, and make sure that they're in good shape... I always do it in person.