I personally don't consider CB Metallics to be the same value as 2gen ones (unless from special parentage like Spriter's Alt, CB hybrid, etc), regardless of the breed and mate, but unless you find someone who don't value CB Silvers that much and is looking for the specific pairing you have, then probably! I had a friend who traded a CB Silver away because she wanted a 2gen from a specific mate before. ^^
For your other question, it depends on what kind of 3gen prize you're looking for and the trader who's trading it. Factors to consider are the birth year of the original prize, the rarity of the pairing, number of offspring the original prize had etc.
A 3gen from one of the original Tinsels or Shimmers from a commonly seen pairing isn't going to be as expensive as a 3gen from a 2014~2015 prize with a pairing that's seldom seen. I doubt you'll get a 3gen prize offered to you unless it's from someone who's seeking a 2gen Gold from Solstice specifically, since 3gen Prizes usually go for more valuable things on average. (: Maybe if you add some more things, like a CB Copper maybe, then you'll get some bites.