Hi Westacott
Welcome to the JY Community! I can understand your apprehension but trust me, there is really no need to worry. You won't be alone, you'll be with a group of 25 or so like minded people, all having the time of their lives in the care of Just You. You will be very well looked after and all the stress of planning and logistics for your trip will be taken care of leaving you with nothing to do but enjoy yourself.
Take it from me - on the Ultimate Alaska trip, you will do nothing but enjoy yourself. If you have a look on the 'Reviews' section of the Forum, or put 'Alaska' into the search function on the top right of the page, you will find my review of 'Ultimate Alaska' from May of this year. It was superb.
Happy to help if you have any questions about the trip that I didn't cover in my review.
All the best
Mandy