Most local gun shops would be able to reassemble and clean it to some level. It will not be fully restored or anything, just reassembled and cleaned. This can be done in a fairly quick turn around time, but that depends on where you live and the shops near you.

If the gun store owner cannot (or does not have time to) do it, I am sure they can recommend someone who can. Look in your local area for a gun store or gunsmith. Usually, any fishing or hunting supply or sporting goods store can also provide good information.

Full restoration is another matter entirely. This (when done right) can be done by a professional, but the wait time is almost a year and will probably cost more than the gun is worth. I do not think this is what you are looking for, though.