I did a teardown (literally) on the wireless one as you can see here:
[guide|5239]
Due to the way it's constructed and glued together I saw no way to repair it. So I popped the keys for replacements . They go out and I have never found a way to fix them. P>S> I bought five new ones just this week : https://www.ebay.com/itm/Apple-A1243-MB110LL-A-Wired-Keyboard-BRAND-NEW-in-SEALED-OEM-BOX/253251445391?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649