Here's the compass as it started out, and the $12.25 repair kit (part C21K, including the fluid, which I'm told is naptha).
First, I took the compass out of it's case, and balanced it precariously on the edge of a chopping board. I didn't need to worry, as it was all totally dry inside... I took the back cover off, using the 4 little screws around the edge, and then took the diaphragm out. I cleaned the edge where the diaphragm had been.
Next, I turned the compass over, and took the 4 little screws out and removed the front cover. I carefully removed the glass, noting that the bevelled edge went at the bottom, with the widest lip to the outside. I used a knife to get the remains of the old gasket out from under the glass, and Methyl Ethyl Ketone (I had a tub from my adventures in prop fixing) to clean the glass up. Carefully, as supposedly it's very brittle.
I put the front back together - it goes gasket - glass (the right way up) - cork. Then the cover screws down.
I turned the compass over, then filled it up with the fluid. The diaphragm goes on with the recessed side towards the inside, then the cover goes on. Now, in a perfect world, you don't knock the thing over when putting the back cover on, and you have enough fluid to submerse the thing entirely when you put the rear cover back on, but I did, and I didn't, in that order. So, I have an air bubble at the top, but that's not the end of the world. I found the best thing to do was put the diaphragm in the cover, and use it to hold the screws in place when I put it on the compass. It was fiddly (hence the spillage), but easier than trying to get the screws in place with the thing all balanced together.
I put the compass back in it's little case, and took the angled foot off the bottom.
Sadly the vibration on the pod extended some cracks in the case, so I had to take the compass off again. Still, like Vince says, if the big mountains are on your right, you're going North :o)