From the catalogs on retrobike, looks like the '91 was offered in turqouise (single color, no fade). It would not have had that stem; looks like someone tried to make a semi-cruiser out of it.
All the years from that era seemed to have downtube shift cables. Just from the bikes I've seen, top-tube shift cabling seems to be the minority. Or at best, it's an even split.
Vintage-Trek has specific Shimano date code decoding, down to the month of the year.