As much as Gomez's contract is the single biggest albatross on the books right now, he probably won't be traded. Not with the Habs contending for a playoff spot, and Gomez dutifully (albeit expensively) centering the second line. Neither will Halak, not given his stellar clutch performances in the Olympics -- that kind of play will be needed in the next 20 games and come April.
No, there is another player who is 1) garnering interest; 2) will free up cap space for an additional acquisition this season; and 3) free up space for next season to sign various RFA's as well as Plekanec next year. That player is Hal Gill.
Gill's value in any one game can be correlated in inverse proportion to the number of skaters on the ice: 5-on-5, he's a liability; 5-on-3, his long reach can take away an entire side of of the ice. Further, his inability to skate is less evident in short-handed situations, esp when down 2 men. During those times, one needs positioning, reach and size more than foot speed.
And for this reason, the Penguins want him back -- and presumably others in the playoff hunt who need help on the PK. The Habs would do well to trade him. His $2.25M cap hit isn't much, but when added with the others that will come off the books next summer, it might be just enough to squeeze Plekanec in, as well as the minor raises due to various RFA's.
Gill may also be expendable because of the play of PK Subban. In his brief stint, Subban showed he was ready for the NHL. He might not be able to kill penalties like Gill, but his offensive prowess may more than offset that. Plus, on the odd occasion he did get beat on the defensive end, he quickly hustled back to get back in position.
There are other Habs who also may be expendable because of Subban, namely Bergeron and Mara. Bergeron would gain more interest because of his versatility and howitzer of a shot.
In return the Habs should be looking for more secondary scoring. When all four lines are clicking, an opposing coach will have difficulty determining matchups (see Canada's 4 game win streak to end the Olympics). The Plekanec and Gomez lines are settled, esp when Andrei Kostitsyn gets back. The fourth line could be comprised of Darche, Metropolit and Lapierre -- size, some speed and lots of grit. That leaves Moen, Sergei Kostitsyn and Dominic Moore for the third line.
While that line is defensively capable, it lacks much scoring punch -- aside from Kostitsyn. So it would be nice to ship Moore or Moen off for an upgrade on the offensive end, preferably someone with a right handed shot to balance out that line. And some size would be nice too.
That's a tall order, admittedly. But some combination of Gill, Mara, Bergeron and/or Moore (and maybe some prospects) could do the trick.