Wurlitzer 7500 Amp and power supply questions

Hello all. I have a Wurlitzer 7500 with the 553 amp and the 554 power supply. Will a model 556 amp directly interchange with the 553? Also, there is a 3200 mfd cap in the 554 power supply, should this be renewed as a precaution? Also on this class of amps is it nessescery to re-cap the entire amp?The 553 amp has a crackiling sound in the right channel only. Is this a common problem with this amp? Will freeze mist help locate the defective component? Thank you for any light you can shed on this. Norman