am curious if this is part of a course that I will undertake
Before you go to ADL, CX will contact you to update your licence details. This stuff will be sent to HK CAD will make up their minds as to what exams you'll have to sit in order to transfer your licence. Note that this appears to be somewhat random - you might end up with loads of exams to do.
Part of the course at ADL is groundschool in prep for your CAD exams. Actually you will do groundschool for ALL of the CAD exams - even if you have exemptions. Once you have finished the finess course you will spend the first 2 weeks or so in HK sitting the necessary exams. No charge to you.
Would it be easier to take an ATP practical test here in the states prior to my course date and then convert it directly
Don't bother.
am also wondering about the medical certificate - and whether I should renew my first class medical here in the states
I seem to remember that you have to have 6 months to run on your medical and IR before you arrive at ADL, but I might be mistaken on that.
Hope that helps.