As you have probably noticed, most modern fixed capacitors no longer indicate the 'grounded' end or the lead going to the internal shielding. At one time, the capacitor's polarity was commonly marked with a band on one end but this is no longer the case ... even though one side is indeed still the shielded side. Depending on exactly what part of the circuit your fixed capacitor is being used in, connecting it in the reverse direction (shield going to signal side), can introduce hum, RF pickup, instability and generally result in poorer capacitor / circuit performance ... and all it takes to determine which lead is which is an oscilloscope!
The second video I viewed shows the process used to resurrect a Yaesu FT-1000MP in truly terrible condition. In a very professional step-by-step process the video shows the logical and systematic approach at making the radio better than new.
Both videos are done by a truly gifted engineer, Paul Carlson, VE7ZWZ, and are exceptionally well done ... the quality one would expect to have to pay for rather than freely view on YouTube.
If you visit Paul's YouTube channel, you'll find a host of other radio and audio-related videos and I guarantee that you will learn something of value ... and probably hang around to watch several more. They are really well done.