Would Also Recommend that you do a Bootable Clone Backup of your current Hard Drive Before attempting any Major Upgrade...
By far the easiest way to make a Backup, is to use something like
SuperDuper http://www.shirt-pocket.com/
or CCC http://www.bombich.com/
Also... For Lion... Check the Compatibility of Third Party Applications you may be using...
See Here:
http://roaringapps.com/apps:table
Lion is a hungry beast...Would also suggest that you Increase your RAM to the Maximum for your computer...
http://www.macsales.com/