1991 Lexus LS 400 Nakamichi Stereo Problem

Electrical problem
1991 Lexus LS 400 V8 Two Wheel Drive Automatic

Hi,

How can you determine whether the stereo problem is with the amplifier or the receiver? My stereo plays and the CD plays, but sounds are all distorted.

1. what is the problem?
2. is it worth replacing with a used OEM Nakamichi?
3. where can I find a used OEM Nakamichi and what can expect to pay?
4. or is it better to replace with a new stereo with blue tooth and iPod capability?

Thanks very much!

Herb
4.