Success! Just as Conmai said, the eyepiece can be pushed out - I made some pics. As a bonus I found out the spares and repair camera had a much cleaner prism than my camera, so I replaced the prism too. On removing the prism, I was quite disturbed by a loose orange cable. On inspection, it has a little c-shaped contact that goes under the screw prism holder screw on one side. I wished I had had a magnifying glass for this, but I managed to get it back in. The first time I put my good camera back together the metering had ceased to respond, perhaps it's the orange cable? I took it apart, re-connected the orange cable with a tiny bit more tightness, and luckily the meter is back! Just a note, I am only doing home repair because my camera was cheap and I'm prepared to lose the whole thing.. for the fun of tinkering. We're lucky to still have legit camera repair individuals who actually know what they are doing. Thanks Conmai for the help!
Lucy