I did that very same transfer a few months back with my website when I decided running my server under Linux was a better option than Windows. I too opted for Ubuntu as the distro of Linux.
The one thing I will say is if you're running your server for more than just testing and local use,
I would seriously consider installing Apache, MySQL, & PHP using the Synaptic Package Manager instead of using XAMPP. Oddly enough, it is much easier to install this way and far easier to keep your server up-to-date since it will tell you when updates are available and can update each component seperately.
Probably the greatest bonus in my opinion is the tool named Rapache, which gives you a GUI interface to manage your Apache server with.
I've written some detailed tutorials you should give a glance at:http://www.myownserver.info/linuxhome/linuxserversoftware.html
If you're using your server just for local stuff and won't be using it publicly, it might be better to use XAMPP since everything is self-contained and easier to get rid of if you decide you no longer want to use it.
Let me know if there's anything else I can help you with.