Haula... a 3rd round pick would do. Or later if that's not available. He is not useful to us. We won't retain for this level of lesser pick, though.
Sissons... ehh... he's not "special", but he's a hard-working physical bottom-6 player... I know we signed him to premium term based on a good season and a lot of projection... he's not "untouchable" by any stretch. But he fits a role. And we don't really have any other player who fits that role any better. I wouldn't trade him for just a pick. It would take some larger and more complex scenario.
Jarnkrok is a good player. But he's also a buddy of some good players who we might want to send a message to, and he's also more of a "versatile utility player" than a really core player. I would trade him for a 2nd-ish return, just to send that message. But he's also cheap and useful, and I wouldn't sell him TOO cheaply just for that sake.
I like Trenin. He's a tank. The Preds aren't using him as much as I think they should. I don't think he has high offensive upside, though. He's a bit of a lumbering player who can bang and chip in, but I doubt he'll ever produce more than, say, Austin Watson did for us. I doubt there are any magic beans here. But you'll still like him. I wouldn't be inclined to trade him, just play him a little more.