Paul,
Sounds like you have learned a great deal on your own about disassembly and re-assembly of a Luger.
[quote] If I pull back on the slide and barrel that front oin loosens and the slide plate starts to fall off <hr></blockquote>That front pin is commonly referred to as a "takedown lever". There is a small spring in the frame that engages grooves in the takedown lever to hold it in the open or locked positions. If that spring is missing, broken or badly worn, the takedown lever can rotate freely, which appears is happening with your Luger, causing the side plate to fall off. This spring needs to be replaced. Tom Heller (Lugerdoc) can probably provide a replacement.
P.S. Welcome to the ranks of the addicted! <img src="graemlins/bigok.gif" border="0" alt="[thumbsup]" />