A few questions - did the passenger side produce sound before you started? If so, then check that the speakers you are fitting are ok, and that you have not trapped a wire down to earth, as this would disable front and rear channels on the head unit. If all appears ok, the measure continuity between the rear of the head unit and the speaker cables (unlikely to have broken both front and rear, but an earth fault would show up here) Failing all that, try connecting the speakers directly to the rear of the head unit to see if the head is actually working or not.
Getting the +ve and -ve the wrong way round will sound a bit wierd to a purist, but from a diagnosis point of view as long as both wires are connected, you should get sound.
Upgrading to BOSE is a fair bit of work, and in my honest opinion, not worth it. Too much wiring and expense to end up with a system that sounded good 15 years ago, but technology has overtaken this considerably, and a good set of aftermarket speakers would be a far better investment