I've never seen a system that will do before-and-after screenshots, but you can track data changes with an audit logging solution. Ray Cologon's version is the most highly-cited: http://www.nightwing.com.au/FileMaker/demosX/demoX01.html
For the admin notifications, you could create a server-side script that periodically checks for new modifications and generates an email.
You could implement a screenshot routine but it would require more work than you would probably want to undertake. It would also require desktop touches. JBante's suggestion is a good one. I don't know Ray Cologon but I have seen some of his Filemaker Videos and he's really good.
Another suggestion would be:
Setup a layout for change requests/submissions.
Users would never have access to the actual record other than read-only access. On the read-only master, place a duplicate of every field you want them to be able to modify. For example if you have NameFirst, NameLast, you would make additional fields called "NameFirstCR" (NameFirstChangeRequest), and "NameLastCR" or some other title that works better for you based on your naming convention.
Use conditional formatting to hide them during normal use. In order to make changes the user would click a "Update Contact" button. Use the button to trigger the fields to appear alongside or in another area and allow entry on those fields. Next you could do a button that would "Submit Changes" and the confirmation dialog might say "Thank You for submitting your changes please allow up to [24-72] hours for the changes to take effect." Next someone might have to approve the changes with one button that pushed all the changes into the target fields or with a button by each field that was changed that might say "Accept Change"
You'd probably have to add a flag to records that were submitted for change and have a script find those for the admin (Maybe that's you?).
Sorry I just noted the date on these posts. Yikes!