There are VERY few gunsmith's around these days that are qualified to work on the old Colt action.
The Colt really IS "different" and it takes someone who's totally qualified to work on them without botching it up.
Another factor is, the Colt's REQUIRE special tooling, and very few gunsmith's have it.
Here's the ONLY people I can recommend.
The Colt factory. No knows more about it then they do, and they have all the parts (for most models) and the highly specialized tooling needed.
Their prices and turn-around are excellent, and the quality is the best.
Pittsburgh Handgun Headquarters
1330 Center Ave.
Pittsburgh, PA 15229
(412) 766-6100
Pittsburgh used to be the Colt factories over-flow center for warranty repairs.
They have parts and the quality, pricing, and turn-around are very good.
Cylinder & Slide, Inc.
245 E. 4th Street
Fremont, NE 68026
(402) 721-4277
http://www.cylinder-slide.com/
C&S is more a custom shop for super action jobs or major custom alterations, but they do do repairs.
Quality is world-class, turn-around is SLOW like all custom shops, and prices are HIGH.
Grant Cunningham gets good reviews, but I haven't personally seen his work:
http://www.grantcunningham.com/
Fair warning: Take a Colt to most any local gunsmith NO MATTER WHAT HIS REP, and it'll likely come back in worse shape than before.
True, there are locals who still know what they're doing with a Colt, but you have no way of knowing who's who.
With the above services there's no doubt about their qualifications.
Again, just because a gunsmith is a master on S&W and Ruger is means NOTHING when it comes to the old Colt action. They really are "different".