If you upgrade to 10.7 you don't need to reinstall, but you do need to delete all existing preferences. This is about 10.9, but the same applies to 10.7:
http://barbarabrundage.com/2013/10/28/photoshop-elements-and-os-x-mavericks/
For fonts, you just install them the way you normally would, via font book. PSE picks up the fonts in your system, unless you're seriously over-fonted, in which case you would need to use some kind of font manager so that not more than a couple of hundred fonts are active at any one time.