I would say go for it. My husband and I are both green with green horses. I understand the risk of that but what's done is done. I wouldn't advise just anyone doing that. I think it takes a huge amount of dedication and understanding to take on a green horse when you have little experience yourself. But as long as your commitment is there.
Just some food for thought though, my husband was really into the drafts when we were looking, so we looked at this 17h percheron/clyde a couple times and finally decided it might be too much for us. We then started considering a cross and ended up with our girl Persia. She is a percheron/QH and is more of a managable size at 15.3 but with the draft features that we love. Like the big head, big feet, and feather.