You could probably get the top off without harm, if you have some knowledge about camera disassembly. One of the innovations in the ST901 was the use of flexible circuit boards instead of wiring. The flash shoe might still be wired- I don't know. If you can desolder and solder, a few wires are not a problem.
For flash, the 1/60 speed on the dial is selected. In auto, any speed displayed below 1/60 will work.