[georgelazenby]

I've brought back to life a couple of faulty 7549s.

The electrical problem will be either a broken coil or circuit board.
Get yourself a 7546 dress watch from e bay. All of the electrical components are a direct swap. The only different thing is the white printing on the green circuit board. You can un clip your micro chip cover that says 7549 and swop that too.
The only snag here is that 7546 prices are on the rise because people are hoarding them for spares like yourself.

 

[georgelazenby]

Tuna gaskets.

I'm sure the only gasket you will need will be a new Teflon crystal gasket.
The crown gasket is a huge donut that fits on the crown tube with a circlip and washer. I bet it will only need lubing with silicon grease.
The crystal gasket is so deep inside the watch I've never seen one deteriate.
I'm sure a modern Sbbn tuna Teflon gasket will do for the crystal
Good luck with the restoration.