I once implemented something like it...
As GUI is concerned, anything goes, being it sliding panels or plain scrollview...
At first run I search for a setting file and read two key values: install date and version and compare it witha version variable hardcoded.. If different check date of release and compare with date of install. This is to know if instal is newer or older than previous installed version. Then I show my "what's new" or my "you are using an outdated version" GUI and refresh the file values as necessary.
I maybe revisiting my (very) old module of this...