can i fix it and if so how to go about doing it
shifting leaver is loose and have to guess the position of the drives & park on 1991 Mercury Sable
You'll want to look at the shifter linkage and see if anything is loose, or if there are any worn bushings.
1 more answer
Block the wheels, turn key to "on" (but don't start car) Crawl under the dash and look up where the shifter arm connects to the cable (move the shifter to help find the connection) above pedals, under dash- there are two gold-colored bolts, make sure the assembly is still lined up, and tighten the bolts (torx) I just had to do this on my '91.