Dude...I feel your pain. I was in a similar situation years ago. The difference was that the company I worked for decided they were going to start selling Mitel. I was an Avaya guy for years and had no experience with Mitel. I was working in the technical support group. I found out they were going to create a Mitel sales engineer position. I jumped at the chance. I did not hesitate. There are little training resources for Mitel products laying around the inter webs. Unless you're a Mitel partner, you won't have much luck. If the new company is a Mitel partner, hopefully they'll have plenty of reference material and access to Mitel Connect. If you're really lucky, they'll pay for training through Mitel's Learning Management System.
If not, you'll face a learning curve but since you seem to have a telephony background, you'll be fine. This forum is probably THE BEST Mitel resource I've found on the web. Most members in here are willing to help anyone out. There smart, articulate and seem to like helping other members by sharing their knowledge.
Good luck
