Hello and welcome! I'm new to the forum as well but have been an Omega fan boy forever.
I recently bought the new 3861 and I'm totally in love with it. I never owned the 1861 but years ago a friend let me borrow a really old Speedy for a while (I'm not sure which reference it was) and the 3861 reminds me very much of the previous version before the 1861.
I just wanted to make a couple of comments on topics that came up so far.
First, I would not feel like you got ripped off because you paid full retail at an Omega Boutique. I've had experience buying from the discount dan gray market websites of other products, not just watches and I'm here to say that there are benefits to purchasing from the Omega Boutique directly. I recently had a mishap with my brand new 3861 that literally made me sick to my stomach (see my thread on the topic) and I was very thankful that I had purchased it from a boutique because the support they gave me and the discounts on the parts to get it back to normal was well worth more than any savings I may have received from buying gray market. So, I guess it's only a ripoff if you're really careful and have the good luck to never have any problems with your watches.
Second, it sounds like you purchased your 1861 to commemorate a significant milestone in your life which you will never forget. I would treasure and cherish that watch and hand it down to your next generation some day. I wouldn't ever sell that watch just to upgrade to the latest. If you really love the Speedmaster, I would just save up and just buy the 3861 because the look and feel of it is great as well as the accuracy of the new movement is phenomenal. There are many reasons to get the new version however, I still would not sell your 1861 to fund it.
Enjoy your Speedy in good health and best regards!
FC