Hoping you guys can help me get this gun back to shooting

Little background, I purchased this gun when I was 12 or 13, I kept my lunch money for an entire school year and took a sandwich everyday instead. I used the money to buy my first gun. I hope to pass this gun down to my kids one day.

Its a single shot 20ga, New Englands Firearms, Pardner-Model SBI

http://i136.photobucket.com/albums/q199/lilreddnek/DSCI0061.jpg

The gun has a small block that slides between the hammer and the firing pin when its fired, and is supposed to prevent the gun from going off if its dropped, but... that piece fell out!!

http://i136.photobucket.com/albums/q199/lilreddnek/DSCI0062.jpg

http://i136.photobucket.com/albums/q199/lilreddnek/DSCI0063.jpg

My first question is: what is correct way to take the gun apart, I don't want to hurt the finish or damage anything else. My second question is where can I find parts, as I am assuming that a small pin is broken. I appreciate any help and let me know if you need any more pictures!

http://i136.photobucket.com/albums/q199/lilreddnek/DSCI0058.jpg

http://i136.photobucket.com/albums/q199/lilreddnek/DSCI0071.jpg

http://i136.photobucket.com/albums/q199/lilreddnek/DSCI0070.jpg

http://i136.photobucket.com/albums/q199/lilreddnek/DSCI0064.jpg

The first place I would look for parts and an exploded diagram is at the Numrich Catalog.
Here is the website:
e-gunparts.com

edit: look at page 3 of the parts

http://www.gunpartscorp.com/catalog/Products.aspx?catid=3626

If it is item 26 (which I think it is) - they are sold out. I would call them and ask, they may tell you where to get them. Those guys are very dry, but very honest when I have called.

I don't know, but you better not get any oil on that cutting mat!