Welcome to the forum.
If you want specific information on the 390, post your questions here. There are probably dozens of 390 owners who visit here, who would be glad to help. If someone is particularly helpful and you want to discuss in more depth, PM them and ask if you can speak by phone.
Limiting your audience to Mystic or Noank means at best one or two forum members.
Also the 350 is essentially the same boat as the 390- name inflation. One thing to check out is if the integral swim platform has been repaired. These leaked and got water logged. Mainship repaired most of them.
And if you want to look at one, there are two in Connecticut listed on Yachtworld. Do a search for Mainships from 35-39'. That will also get you a few 36 sedans also, but it is really the only way as some listings don't use the 350 or 390 designation.
And finally if your budget is a little higher, and if you are a couple, consider the 2005+ Mainship 34T. More room than the 350/390 due to wider beam, but only one queen size berth forward.
David