Senior with 2 questions: Speedometer Capacitors or Speed Sensor??/Also Instrument cluster light question

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Hello. We have a 1995 Corolla Base model/1.6L, which we don't drive too often (keep it for when our other car is in the shop). Anyway I have 2 questions/issues I could use help with:

 #1)  Last time we drove the car we noticed that the speedometer wouldn't work until we got to about 50+ MPH - then the speedo would jump up to 50 or so MPH. As long as we stayed above about 50 MPH the speedo would register a speed. Once we dropped below 50+ MPH - the speedo would drop to zero. Was told it's probably the 3 capacitors on the back of the  speedometer. So I changed them out but it still doesn't work?? Could it be the speed sensor? Or does the fact that it starts working when we hit 50+ MPH eliminate the speed sensor? ** I should also state that when the speedo does start working - it speed is off (my wife drove behind and when the speedo starting working and saying 50+ MPH, it was off by 10 more so MPH??  (Of course, since I'm old and my eyesight is bad, it's possible that my soldering isn't that good or maybe I don't have the polarity correct on the capacitors??)

#2)  Is there a way to bench test the lights in the instrument cluster? I have been trying to upgrade all the instrument cluster lights to BRIGHT LED lights (easier for us old folks to see) and no matter what I do, some don't seem to work?? I' used 'supposed' non-polarity LED's.  I should say that I'm a disabled senior and it's quite a pain to keep having to go out to the car to remove/replace the cluster to keep changing bulbs. I know there's a guy on eBay who sells clusters and he has rigged up a bench tester - which also tests the speedo, but he said it cost $500 bucks to build. I have to believe there's a way just to illuminate all the bulbs on the cluster somehow.

As always, let me say in advance that any and all help, advice, and suggestions are GREATLY appreciated!!