Yes, Left hand threads are OPPOSITE of normal right hand threads. In the 50's/60's chrysler thought it would be cute, for thier lug nuts to use LH threads on the LEFT side of the car and RH threads on the RIGHT side of the car. Everybody wound up stripping these out trying to get them off
Yes, the tensionor pulley will begin to squeek and squeal, thats why this car was brought in. A mechanics stethoscope will help to pinpoint it, but if you can wiggle it side to side, then its probably going. The Stock one uses a good quality NTN bearing, but when you go to get a new one you will most likely get this cheap POS taiwanese bearing, so see if you can get one from ford.
The bolt that holds the tensioner on uses normal threads, its the bolt that holds the pulley itself on the tensioner that is LH threads. The pulley bolt needs an 18mm socket, but you will need a torx socket to get the tensioner off the block. The whole job took me about 30 minutes, including sitting there like a dumbass before figuring out it was LH threads, and waiting for the part to arrive. You will need either a long breaker bar or a serpentine belt tool to get the belt off.
The job is easy, you can do it in a little while. Practically no tools required.