You never said how the oil pressure gauge is "Acting Up", but...the oil pressure gauge on Gen-1 Sport Tracs is just an idiot light and the sending unit is known to be defective, especially when the weather gets cold. It sticks and shows no oil pressure, and a few minutes of idling the gauge will register normal pressure.
The idiot/gauge will jump to the normal operating range when the sending unit senses about 8 PSI of oil pressure. If the sending unit sticks, which is all too common, the gauge will show no oil pressure at start up and you will probably get a "Check Gauge" light. After a few minutes of idleing, the sending unit will unstick? and oil pressure will register on the gauge as normal.
The only solution is to replace the sending unit, or just ignore the gauge? I personally do not recommend ignoring the gauges, so I would opt to change the sending unit. My Sport Trac had the same problem, and the Sending unit was replaced by Ford under warranty, but it was only a few months old when it started acting up.
The alternative is to add an aftermarket mechanical or electronic oil pressure gauge that is a true gauge, and not an on/off idiot gauge.
...Rich