Re: 94' Explorer...in a mechanical age, what i would have called "advance problems"
I'd replace the IAC (idle air control) and TPS (throttle position sensor). They should help mitigate some of the problems. To have ten engine codes, that's a lot to be stored. I imagine that more codes were stored, but they've since disappeared. The engine light will go off only if no more codes pop up, or you've started the vehicle at least 50 times.
Replace the PCV valve as well, along with spark plugs and wires, and the sensors mentioned above. This should help make the vehicle more livable while you make deliveries. Total cost should be around $250 if you install the parts yourself, or $400-450 for a shop to do it.
Another thing you might want to consider, is changing the thermostat. This has a few benefits and a negatives. First, the stock T-stat is 195F, You can install a 180F unit (local auto parts store should carry it) and this will lower the engine temperature. It can increase engine life, reduce engine knock/ping that is generally associated by high temperatures. The only downside is if you drive the vehicle in the winter, below freezing, the 180F stat won't keep you toasty enough in the cab.
The pros definitely outweigh the cons. I run a 180F stat in my Durango during the summer, as it helps a lot when I tow my trailers. It takes me 20-25min to change out and costs me $10 twice a year. It's more than worth the investment!
'00 Durango R/T 360ci 290hp (modded); 138,500m
'06 Pontiac G6 GT 3.5L 220hp; 44,000m
'12 Chrysler 200 Limited 3.6L 283hp; 13,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!