If the plug wire fixed the misfire, the SES light will go off after so many engine cycles (forgot how many exactly). Or you could go somewhere that has a code reader, like a autoparts store, and have them clear it.
The temps sound high but might be normal if you have the stock fan setup. Even with the 160 thermo the stock fan clutch is still only going to engage when it gets that hot. My wifes stock Tahoe runs about that at idle with temps like they have been here in Austin.
'02 1500HD, 6.0L, magnacharger, 2000stall, custom magnaflow with electric cutout, E-fans, Nelson custom tune, Auburn LSD.
'79 L82 vette, Summit 355, Dart Pro1 heads, Comp 274 cam, Holley TBI, Built TH350 with 2500stall
'93 Blazer, full size 2dr 4x4, new project.....