Hmmm, it's a good start! But I wouldn't accept it as is.
For example, Gallagher's recent 82-games pace goal totals (13, 29, 24) are almost identical to Eberle's (20, 29, 24), except for one down year this season. Gallagher's compete level and playoff record is way significant to Eberle's, and he's quite often described league-round as a coach's dream in terms of his work ethic and feistiness. So I'd say Gallagher is likely a little more valuable than Eberle, purely as a player. However, when you factor in contract considerations, that's where the real concern shows. Gallagher is signed to a very team-friendly long-term contract, while Eberle is signed to a very non-team-friendly short-term contract.
Essentially, we're going to be giving long-term good for short-term less-good. After two years, we won't have the space to re-sign Eberle to the size of contract he's used to, though we will still have space for Gallagher if we weren't to trade him, even with Price's contract coming up.
As for Galchenyuk for RNH, I would personally prefer to keep Galchenyuk and properly develop him into a center, but that doesn't seem to be what management wants. So assuming a trade is inevitable, I would be lukewarm to this trade. Galchenyuk has 1 more point than RNH in 21 less games. That's a significant leap... In a one-for-one, we would lose the trade
Anyway, back to the trade you proposed. I did say it's a good start, so here's a counter-offer:
MTL Gives:
Andrew Shaw (Half salary retained over 2 years: 1.95M per year, total 3.9M retained)
Brendan Gallagher
Alex Galchenyuk
Michael McNiven (elite goaltending prospect, which you lack)
2017 2nd round pick
EDM Gives:
Ryan Nugent-Hopkins
Jordan Eberle
Jesse Puljujarvi
So, what's your reply to this? I'm well aware of the value you place on Puljujarvi, as am I aware of your absolute need to dump Eberle to clear space for McDavid, Maroon, Nurse, Shlepychev, Benning, Caggiula.
[I mean it all in good fun. Happy Armchair-GM-ing!
]