I believe for me when doing this running the configuration wizard after changing the machines name and joining it to the new domain fixed issues with the website.
No love, i'm still getting website error 500 when I try to view the site after the change and running configuration wizard. I'll keep playing around and post up what I find out.
What is the URL you are using? Is it a FQDN or a short name?
Have you tried targeting it just by IP address?
If so what are the results?