I have a "Do what you love" philosophy on this, so if psych nursing is calling your name, go for it. I've worked in different areas through my career, usually briefly, but always end up back in psych.
Now, having said that, I need to respectfully disagree with those who say med surg and psych are totally different and you don't need med surg skills if you are going into psych. You will have patients who have bipolar disorder and type 2 diabetes; major depression and high blood pressure; and yes, schizophrenia and pregnancy. Not only that, the newer medications are effective in helping to manage symptoms, but they also carry a risk of metabolic d/o, seizures, thyroid and cardiac dysfunction. Some increase the risk for various other disorders, like agranulocytosis. If you are going to work with persons who have substance abuse issues, you most certainly will run into co-occurring liver disease, neuropathies, GI problems. You are a nurse: your role will be to assess, advocate, educate, keep your patient safe, help them return to a higher level of functioning. If you are concerned about losing your skills (I'm guessing you mean the tasks like starting IVs, dropping NG tubes etc) then maybe consider a casual position on a med surg unit. Or take a refresher course if the situation dictates.
It sounds like you are thinking this through, and that is a good thing! Good wishes to you as you continue on, and make the decision that makes the most sense to you.