I don't think it's a pipe dream.
By giving yourselves 5 to 10 years to get up to speed, you should have no problem reaching Alaska.
Many have done what you are deaming.
Taking "On the water courses" is a good start.
Chartering or Time Share boating is also something to consider.
But the best way is to buy a boat and start taking small trips. Start with a small boat if your budget is small. Too many people in your situation delay purchasing a boat because they have the perfect boat selected but it is out of their price range. Some end up buying the perfect boat eventually but some unfortunately never do.
Until you buy that first boat to learn on, you will not know what you want or not want in the perfect boat. You can research all you want but, boating is the best way to learn what is important or desirable to you.
I've had clients buy their first large boat and after taking on the water training and cruising for a while, decide boating is not for them. Some of these clients purchased new 40 to 50 foot boats and sold them in a short time, at a loss.
Join a yacht club if you don't have any boating friends. Experienced boaters are a good source for knowledge and maybe a boat ride.
Hire a buyers consultant.
"My worst day working on the boat is still better than my best day at a job"