I think this team needs to move at least 2 players, because the young guys are showing they deserve to be playing right now and they can't even be up in the NHL with a healthy roster. The Penguins have almost no roster flexibility, they have 21 skaters who require waivers in the NHL and the Penguins don't usually waive NHLers. You need to move a few of those guys so you have roster spots/expanded roles for guys like Lafferty, Marino, Simon and ZAR.
When healthy, the Penguins appear to have something like this right now:
Guentzel-Crosby-Simon
Galchenyuk-Malkin-Rust
McCann-Bjugstad-Hornqvist
ZAR-Blueger-Tanev
Kahun-Lafferty
Dumoulin-Letang
Pettersson-Schultz
Johnson-Marino
Riikola-Gudbranson
Ruhwedel
You only need a little bit of cap space, so moving Gudbranson is probably more than enough for what you need. However, you still need to move 1 extra player to become roster compliant and you need to move a regular forward to get Lafferty in the lineup (if you want him in the lineup). That plus the fact that you're going to have to move Bjugstad eventually are the big arguments for moving Bjugstad IMO. Moving Ruhwedel in addition to Gudbranson is probably the smartest roster move, but I'd be a little concerned with taking that much away from their RD depth and Lafferty isn't in the starting lineup with those moves.
Edit: I'd also throw out the idea of moving Kahun and Gudbranson for no long-term cap back. I think you can move Gudbranson right now, but you probably only can move him in a money for money swap. However, I think Kahun may be an enticing enough addition to be able to move Gudbranson for rentals and draft picks, similar to the McCann/Bjugstad trade. Even with his struggles this year, he's still on an ELC and had a solid rookie year last year.