Why do you need to get a new domain? you can reuse the old one surely.?
Can't you export the data, keep the old media directories, and import it all into a new install?
I've only just updated to 4.2.x because of my worry of trying to upgrade ruby, which wasn't a smooth process, and I've probably got 3 damn copies of ruby in different parts of my filesystem, but apart from that, it was a smooth upgrade after that fiasco.