Not to give the wrong impression, on mine the removal of trim ring & glass was very easy. Just have to be careful because of some delicate parts, no ham fisted crunch & rip stuff.
There were I think 3 little metal tabs on ring protruding from back of instrument case, bent over to hold chrome ring. Careful straightening, then some gentle prying with a small screwdriver on the trim ring, which is sort of crimped or swedged on, releases ring. Seems to me there's 2 screws in speedo dial face holding it to movement behind.
Don't know about prying off the needle, never tried that part, could get weird or disastrous. To get just the ring & glass off isn't that difficult and with reasonable care is real easy.
the 3 tabs were easy but those are just on the other gauges. The speedo chrome is crimped all the way around and has no tabs. they did this so tampering with the odomoter was not easy. I managed to get the chrome ring and glass off then the unit can be serviced. I did put a few small ham fisted dings in it though. The chrome is not all there anyway. I am gonna switch to white gauges after a while I think or if I run into a deal on a factory tach for the round gauges I might go that way.