IAG -- International Alpine Guides: Going with a professional guide service on your first time up the Mountaineers Route is a great idea. They will use the best route for the conditions, so you shouldn't have any trouble.
1. Current weather is cold and dry. The snow that came in December is about all there is, so should be well-consolidated. Everyone is hoping for more snow, but so far there is nothing in the forecast.
2. The Final 400: I'd expect a guide service will rope up all their clients. At least that is what I have always heard. It is the usually the inexperienced without any training that have issues on that section. Pay attention to what the IAG people are telling you.
3. Front-pointing: You will likely need every method available, but I've always found using crampons comes pretty naturally. You've been up Shasta, so you have likely spent quite a bit of time already with crampons and ice axe.
4. Same clothing as Shasta.
5. Ebersbacher Ledges: If there is enough snow, winter ascent goes right up the ravine over the snowpack, skipping the ledges. If there isn't enough snow the ledges are pretty easy.
