Fifteen years ago I tried going from sailboat to planing trawler. Sold the boat six months later and bought a motorsailer.
The problem is that planing on an 40ft boat isn’t comfortable in even a small offshore sea. There’s a lot of noise, slamming over waves, and spray covering the windows with salt. It’s hard to walk around or go to the head without slowing down. My wife hated it.
Worse, a planing hull design often isn’t good at a comfortable 7-8kts. The bow goes up and there’s a big wake. It’s designed to “get up on plane”
The trip becomes about “getting there” rather than an “enjoying the journey”
Even if you run slowly, high horsepower engines are MUCH more expensive to maintain than little sailboat/trawler diesels and few owners do their own work. Check the cost of an impeller.
The only caution for a sailor moving to a displacement trawler is they roll offshore. There’s no sail pressure to keep it steady. I have trawler owning friends who dread offshore trip like going to Maine because of the roll. So in shopping I’d ask questions about how much it rolls. Boats with flatter aft sections typically roll less.
Of course, stabilizers fix the problem but they are expensive and break down frequently.
Finally, I would think many times before buying a steel boat. My steel boat owning friends are constantly checking for rust, grinding down to bright metal, and repainting. And his boat is less than 10 years old. If you live on the boat full time, you can keep up with the rust but that doesn’t sound like you.