rpm's dropping and recovering

My wife called me this morning concerning her car listed above, I believe it is the 3.1L engine but will confirm that later if it makes a difference. She was driving down the highway when suddenly she said the tachometer dropped to 0 and then recovered a second later. She said it "felt" like the car was shifting very hard, and that it did this multiple times. She pulled over into a parking lot and even when in park, it would continue to drop to 0 and recover. I am asking for some opinions, to me it sounds like fuel pump or fuel pressure problems (maybe even a clogged filter?). I am open to suggestions on what others may think it could be. I just hope it is not the fuel pump because those are a pain to replace. TIA.