Two questions in one post

[infinitewill]

This is my first post and I am not sure I am even in the correct forum.

I own what I was told is a 16800 series Submariner from the jeweler I purchased it from 20+ years ago. This is kind of a long explanation so please bare with me. About 19 years ago I did something that I now know was incredibly stupid, I wanted to have my watch face and bezel insert refinished in a non-factory color. After contacting literally dozens of watch dealers, I was told that no factory authorized Rolex dealer could touch my watch once altered with a non-NOS part or finish. I contacted E.G. Marshall in Scottsdale, AZ and they told me they had the ability to refinish the face and insert in a deep Royal purple finish and after several month I got my watch back in what was an aftermarket Blue and Stainless face and insert PLUS they kept the factory parts. Live and learn from my mistake I guess. Understand the work they did was gorgeous, just not what I asked for nor paid for.
Fast forward 18 years; I would like to return my 16800 back to factory correct however I am challenged as to what face was on the watch originally. I have the original box, registration papers, anchor charm, seal hang tag, certificate of ownership (I think that is what it is called) even the original Rolex passport folio that came with it. Is there a way of checking my serial number to identify what the of face I should look for? Also can any of you recommend a trusted firm to help me do the restoration?
I am asking this because I was recently told that the value of my watch has been halved because of the alterations and I would rather return it to original condition.
Any thoughts other than YES, I was an uneducated fool for altering my watch? 😀

Thanks in advance!

Will In O.P.