If you installed it via the Control Panel “one-click” installer, you can also remove it from there.
If not, you can simply delete all the files and directories that comprise Gallery2. Exactly what you delete depends on where (in your directory tree) you have it installed.
To completely delete all traces, you will also want to delete the associated database, and that can be done from the Control Panel–>Goodies–>Manage MySQL screen.
As for recommendations for “simpler” gallery programs, there are literally hundreds out there (you can check hotscripts.com), though if you are “extremely new to web design”, unless you have a reasonably good background in *nix operating system and MySQL, you may find other programs installations to be difficult (one of the the reasons DH provides Gallery2 as a “one-click” install is to shield you from this.)