I know this is a long time after you posted it but...
I also have a 3400, I have the original technical documents which have the schematics, let me know if this is still needed.
As to the screws not budging, try heating with a torch, they probably have too high a grade of Locktite applied.
Have you been successful in your conversion?
- George Lawrence Storm, Kenmore, Washington
George Lawrence Storm, Kenmore (Seattle), Washington
Inventor, Machinist, Macintosh Applications Developer, Videographer