Struts in the front, shocks in the rear.
Struts.
Get the original replacement shocks from the dealer/mopar, everything else will be either too stiff or too soft.
The Grand Marquis has shocks, not struts. They are simple bolt on parts.
There is a difference between the two, however your 97 Jeep Grand Cherokee has a modern version of the conventional shock system, where the shock and coil spring are separated under the live axle. Good news is anyone with an extension, socket wrench, channel lock pliers and 13 14 and 15 millimeter sockets can change them out in a matter of minutes.
Replace the shocks, or struts if equipped.
By removing the bolts.
No.
No, you will need more than shocks to get 3 inches of lift.
Bad Struts
Depending on the type of shock, every 1 to 3 years.
I'm not a mechanic but I had a problem with my 1999 Jeep Grand Cherokee lift gate not closing properly, seemed to move to the sound causing a noise. I replaced the lift shocks and the problem disapeared