Welcome to Bodhi Linux.
You could try the installation straightforward on your X31- an excellent laptop (I've owned one or two of them) - but you need the legacy version of Bodhi. Once you've seen what's all about you could try to upgrade your Mac.
As a slight coincidence I've also started using Linux because of a Thinkpad X (I don't remember if it was a X22 or X31). At that time Ubuntu just changed their kernel and the non-PAE machines were no longer supported and that's how I found out about Bodhi from some post in a forum.
- Oblio likes this