Good man!
Firstly, dates Practice week starts 16th August, and racing finishes on the 29th August.
Marshalling: http://www.iomttma.com/
Check dates and availability with them, and if you are coming across for training, let me know as I can find you free accomodation.
You will thoroughly enjoy the Manx, I am sure, and I know you will benefit yourself and others by getting the marshal training and putting it into practice... you'll certainly be glad you did.