Weather and conditions are impossible to predict weeks in advance. Best case, the MR could be doable as a day hike (I did it 1-13-2014). Worst case, deep snow and avalanche danger could make it impossible. The truth will probably be somewhere in the middle.
In the winter, most parties (guided and private) bypass the E Ledges on the left side of the canyon. You will probably do some front-pointing in the couloir and on the Final 400. I think that most guide services rope up for the steeper parts of the couloir and set up belays for the final 400.
I’ve never climbed with IAG, but I climbed with one of their guides, Brian Biega, when he was with climbing legend Doug Nidever. I had a super day ice climbing with Brian. You should be in good hands.
IAG should give you an equipment list. Just bring whatever they recommend, possibly fine-tuning it a little to suit your personal preferences.
Good luck. Stay safe. Have fun.