I changed the front shocks with KYB Gas A Just shocks. Couple of notes. I have a Ford Explorer 2000 XLT 4 door 4x4 AWD.
First in getting that top nut off the top shaft, I bought the Truck with the original OEM shocks and it has 146K. A day prior I liberally applied PB Blaster, and again an hour before the project and again during disassembly. It was still difficult, but not as much as it would have been without it.
When you take off the old shock and install the new one, the new shock will appear shorter, you will have to Jack up the wheel assembly until the shock rubber mount reaches the lower hole in the top shock shaft. Make sure you use the 5/8" side of the new rubber bushing. This will mount exactly. KYB provides all new hardware.
As for the Ride the new shocks were night and day. I have better control of my truck, and it makes tighter turns, plus it no longer nose dives. Since the OEM shocks were pretty much wasted, these new shocks were just what I needed and saved about $$ in labor.