Engagement/anniversay ring work?

(If this belongs in Deal Discussion or Off-Topic, please move. Thanks.)

I have gotten a few estimates locally to fix my wife's engagement and anniversay rings. They seem pricey, but then again, I'm cheap

I would think that there would be places to send the rings away to be fixed, but immediately the red flags fly up:

1) risk of loss on an irreplacable item
2) trustworthiness of the craftsman

Am I thinking clearly on this?

One local shop told me that they could fix the engagement ring (adding more gold where it has worn thin, replacing the prongs that hold the diamond in, for approx. $130). Another told me that that approach would be a waste of time and money because it would not look very good, would just need to be fixed again in a few years, if you didn't lose the diamond anyway in the meantime. Cost to replace entire mounting ~$500.

The engagement ring has too much sentimental value (it was custom-made, and therefore harder/more expensive to find a replacement mounting/setting) to mail away.

The anniversary ring I'd risk mailing away (one of the diamonds was lost and the settings are loose). Both local places want to charge ~$350 to repair that one.

Ideas? Thoughts?

I for one would never do mail-order jewelry repair unless it was going back to the designer, such as Tacori, Diana, JB Star, etc.

Are these local places that you found reputable family jewelers, chain jewelry stores or your typical foreign-run mall jewelry repair stands? I would steer clear of the final 2 and find a reputable, family-owned jeweler.

Without seeing the ring in question, $130 seems reasonable for the first one.

What is wrong with the one that they want $350 to repair? Does that include the cost of a replacement diamond? Also, what is the value of these pieces through privately appraised?