Buyer or seller?
Uh, a little of both? It may seem odd to even suggest a team that's contending for a home playoff seed in the Eastern Conference could be a seller, but the Habs remain a team in transition, and if GM Marc Bergevin can find a taker for some of his anvil-ish contracts (hello there, Rene Bourque), it's hard to imagine that he won't. Bergevin's also on the lookout for the missing pieces to his team, so would be willing to buy for the right fit, though he's not inclined to part with prospects or picks unless it's a killer deal. The Habs GM is also a noted trade deadline skeptic, so it would be out of character for Montreal to be a big player.
The Habs' braintrust has been striving to get bigger, but their real need: a minute-munching, physical, top-pair lefty defenceman to play with P.K. Subban (Ryan McDonagh sure would have looked good in that spot, but hey). A hard-edged righty puck-mover for the three or four hole would also be good. One or both would allow a reshuffle of the blue-line, resulting in Alexei Emelin or Josh Gorges (or both) being dropped to the third pairing, and Douglas Murray shuffled into the pressbox. But with good prospects in the pipeline like Jarred Tinordi and Nathan Beaulieu and the high cost of worthwhile assets, it's hard to imagine the Habs overpaying. The other thing the Montreal needs is a big, dynamic right winger with 40-50 goal potential. Good luck finding one of those. Organizational depth on the left side is thin, so if there were a top-nine left winger on a decent contract out there, Bergevin would surely look at him.
On the block
It's an open secret that Bergevin has been trying to flog the inconsistent Bourque, who has two remaining years at $3.33 million. He's less likely to move, though, than a player like rugged penalty-killing ace Travis Moen, a former Stanley Cup champion and the kind of character guy contending teams love to acquire at the deadline. The Habs would surely listen to offers for captain Brian Gionta, who is now essentially a defensive specialist and has an expiring contract, but the market for under-sized forwards who don't score a lot isn't great. It's hard to imagine Montreal would move defensive keystone Andrei Markov (how would they replace his passing and vision?), but he's 35, about to become a UFA, and would likely command a steep ransom or picks, prospects and roster players. A move can't be ruled out even if it's highly unlikely – the added complication is Markov has a limited no-trade clause. Same goes for Tomas Plekanec, another player who could net a handsome return, but almost certainly won't.
Money. The Habs have plenty of cap space at the deadline, and they could theoretically afford to make a move to acquire a Thomas Vanek or a Matt Moulson. Don't bet on it, though. Montreal is about to call in the armoured car service to pay Subban, who is due to become an arbitration-eligible restricted free agent in the summer, and will surely command an annual salary in the $8.5-9 million range for the next six or seven years. The Habs also need to make a decision on centre Lars Eller, whose contract is also up in the summer; the Dane hasn't been able to generate much offence since linemate Alex Galchenyuk went down with an injury (he has since returned but on Plekanec's line) but he's still young, he's big, and he's got a two-way game. So while the Canadiens have the resources to make a big acquisition in the near term, it would hurt their cap picture long-term.