Is it possible to resurface (or veneer) the existing crown work?

Unfortunately, there is no way to resurface preexisting veneers/crowns without compromising the structural integrity of the veneers/crowns.  My best advice to you would be for you to have only some of the veneers/crowns redone, the ones that show in your smile.  Just make sure that you view the before and after photos of the new dentist that you select, so you will have a pretty good idea of what type of outcome to expect.  Good luck and I hope this helps. Follow me if you have more questions.Sarah Thompson, DMDReal Self 100

Depending on the material the original crowns were made from it may be possible to resurface but it is probably best just to replace the crowns.

In general, the only time I would recommend to my patients to resurface a crown with a porcelain veneer is if it is part of a long bridge. In this scenario, replacing an entire well-fitting bridge that is cosmetically acceptable due to a small porcelain fracture on one tooth is extreme. However, if the bridge is ill-fitting, older, cosmetically failing, or any other possible issue is present, I recommend replacement. The restorative ceramics available today are much more lifelike and much stronger and more durable than what was available even 4 years ago. I recommend you get a second opinion and see what works best for you, good luck!

Without a photo it is impossible to tell you what can be done. It is possible to do porcelain veneers over existing crowns and bridges, but there are bite, material and aesthetic considerations that may make it inadvisable or even contra-indicated.  Post photos, xrays and pics including your bite.