Thinking about get a free script. Then buy a more expensive better script. That way i can spend the money i have now for links etc. 1)Can i delete the free script 2) how easy is it
As said, the issue will be if there is any user contributed content and migrating it over to the new script/ db format. Worth looking around to see if there any conversion tools before deciding on which scripts to use otherwise when your site has become popular you may find yourself having to start from scratch again
Deleting a script is just as easy as deleting the files from your server. But when you upgrade to new script you might want to retain the content, you might need to retain old urls with PR, user base and many more thing. So if you are upgrading to a newer version of you existing script, or if the new script provides an upgrade path for your old script than it might be easy to upgrade,otherwise it can be a headache and in some cases it might not be possible to upgrade. So before you take any decision make sure that you will be able to upgrade in future.