Finally, got in touch with the person responsible for selling the unit.

So far based on what he has told me, the unit needs service bad.   It's been sitting on the basement for more than a decade.  It's an estate item.

He offered to send it to a technician for test for additional $50, which is reasonable.

My question is:

The caps in the pre-amp and amp must be pretty bad, and I want to convert this unit into a more or less component item.   I want to be able to use outboard pre-amp and amps.  

Would this cause problem with the operation of this unit?

There is a good chance that these capacitors are ok. They used differant iems in these machines and so they are not as prone to problems as later stuff.

The power supply caps may need replacing, but you may well find your problems will be confined to hardened bearing grease and belts that need replacing.