It's a major PITA to do. As Sharps said you need to drop the front axle to gain access. This means pulling the driveshafts, which means seperating steering components, lower ball joints, etc.
The oil pump pickup is protected by a screen which should stop debris from being picked up and circulated. Personally I wouldn't pull the pan for a few small plastic pieces. Look at the old sensor and try to figure out how much is actually missing. You may be able to flush the pan somewhat by adding sone kero / diesel to the oil before changing it to thin it out. Screen your old oil for pieces that have been flushed already.