Get 2 or 3 written estimates first and see what the Pro says about the insulation. Have that priced out separately IF it's asbestos. Then, assuming it is, have an Asbestos Abatement Specialist give you a price.
In short, BEFORE you do anything, as you already know, find out what that stuff is. It may be harmless but I can't tell from here. Personally, I've never dealt with asbestos around air ducts for obvious reasons - IF it gets into the Ventilation System, then you're breathing the stuff!!! I have to assume it's not but you never know.
My best to ya and hope this helps.
Jay J -Moderator
PS: IF it is asbestos, I'd make an appointment to see a doctor that's familiar with diagnosing asbestos-related ailments.