Where's the serial numbers on my 20yr old Bostitch framing nailer

SOURCE: Paslode 5300/75S Framing nailer

Soory It is a roofing nailer not a Paslode framing nailer. ended up replacing the main valve. all is well now. thanks

SOURCE: Stanley bostitch coil nailer gun

check the safty shaft and see if something could be under trigger safty causeing it to fire.

SOURCE: n80sb-1 stanley bostitch framing gun.

Yes your nailer will drive other sizes of nails. For info and parts go to www.bostitch.com and look for the support tab then select service parts. Here you will find parts list and manual. To remove the tva11 trigger valve remove the retainer pin (the pin is 3mm) for the trigger and remove trigger. Next remove roll pin/pins that retain trigger valve. Use heavy glove to catch trigger valve as you apply air pressure to gun. The valve could pop out with great force so try lowering the pressure to gun. Before installing the new valve, check the opening for sharp edges which will cut orings. Good Luck and email if you have more questions.

SOURCE: Rebuild kit for a ISM sold by Hilti coil nailer model RC234B

I did some extensive research for you and found:
This Link to ISM FASTENING SYSTEMS
http://www.ismsys.com/ToolInfoRequest.aspx
If you Look Under the Category: Coil Nailer Roll 15234 Open That PDF and It shows an Exploded View of Your Gun, and Available Parts. I think you should be able to find a Air Tool Shop in your Area That Specializes in Carpentry Air Tools and Probably Save a Bunch of $$$ on a Rebuild...However, Here is The Address & Ph. Number for ISM, and You could Call and get an Estimate of email them too.
WESTERN OFFICE
AIR NAIL
SOUTH GATE, CA
800.479.6455
Sounds to me Like all you need is a O-Ring Kit, and Perhaps a New Driver.
Good Luck, I hope all this Info works for You.

SOURCE: I have a Stanley Bostitch finish nailer n60fn its

The fix it replace the trigger valve. It is a 5 minute job and seems to be a pretty common problem. Bad news is they seem to run about $30. I believe the bostitch # is TVA6