it's easy, you might even be able to adjust your current linkage.
there are three retaining pins and a 13mm bolt holding the linkage to the steering column, frame and tranny. you could loosen the bolt, put the tranny in park (flip the arm on the tranny all the way forward), then put the shifter in park and tighten the bolt.
if that doesn't fix it then you'll need to repair or replace the linkage.