Dont expect any halfway decent performance without a total recap and replacing out of tolerance resistors. Then do a complete socket voltage and resistance check.
Then you are ready for the real problems!
When you do the RF section caps also do the silver micas and resistors, its not an area you want to work on twice. Im about ready to start on another SX-28 for a customer this week, its not bad after the first half dozen or so.
Carl
KM1H