Restoring old wideband radios is almost never financially advantagous to you and what you end up with is an old radio that works but far less capable than newer equipment at a greater cost.

Yes if there is a compelling reason such as a treasured old radio, then fine go ahead but if your goal is to learn to fly then don,t waste your time or money.

If the radio you mentioned (PCM 9) is in fact an Airtronics Spectra PCM 7 or 9. Then this radio is probably narrow band and this one may be worth messing with. The older stuff save yourself the trouble.

John