I'd have a shop do the diagnosis if you're not willing to do it yourself. Then trust their diagnosis, and hold them to the repair.
The first step is to get a mechanical gauge on there and watch the pressure. You may have an oil pump problem, or you may have worn mains, resulting in low pressure. It might just be a loose connection at one of the sensors or a broken wire somewhere too. Did you replace the sensors with the correct part number OE sensors (installed in the correct locations), or cheap aftermarket parts?
You could ground the sensor and put a gauge on it I suppose, but I've never been a fan of in-car oil pressure gauges. They really make a big mess when that little plastic hose breaks.