If it is a parts replacement, do it yourself. It is a great educational experience. It really builds self exteem. If it is a problem that you can't figure out, post it on here and let the members help you figure it out.
I suggest using a gunsmith to do machine work or to make parts that you can't find anymor. Machine work such as opening up chokes, threading barrels for tubes, etc., is better done by an experienced gunsmith. Almost everything else can be done by you.
I have a gunsmith that tells me step by step how to do most repair jobs that I can't figure out on my own. His email is
kirbythegunsmith@hotmail.com. I had a problem last year that was bugging me on how to replace an extractor. He sent me step by step photos at no charge except a thank you. I'm sure that kirby will do the same for you. He sends out an email newsletter from time to time at no charge that is most helpful. I don't know where he is located but I'll find out if I need a barrel threaded or a choke opened up. Anything I can't figure out with a post on here. So far, all I've had to do is tell you guys and someone has had the same problem and gets back to me so that I can repair it myself.
If I needed a gunsmith it would not be a local parts replacer. It would be one of the gunsmiths registered on here or shotgunworld.com. These guys are reliable and you don't have to worry that their work is first rate. Most of the local parts replacers, come "gunsmiths", don't have the precision lathes and milling machines to make obsolete parts and thread barrels straight. They have a bin of parts that usually holds every part except the one you need.
Doing it yourself is a great self esteem builder. Thousands of members on this site are ready to jump in to help you figure out how to do it yourself. Many problems have been figured out for me when I disassembled a gun I'm not familiar with and couldn't determine which part went where. Good members here that have had similar problems ready to help.