I guess how difficult it might be depends on what you are willing and able to take on board and how much money you have to throw at a project or how small your budget is. Having a sizable garage helps a great deal as does having a helpful friend.
This could be a straight forward project for you. Your friend might find it a little more like hard work though.
I've never built a 'kit car' but I have built from scratch and converted some vehicles in my time.
My experiences might differ a great deal from the average kit car builder.
A helpful grown up will come along eventually.