My 1999 jeep cherokee sport will shimmy after hitting a bump at 55 mph. should I be replacing suspention arms and bushings?

Before replacing things you don't need to, Have the front end checked, or check it yourself. Jack up each wheel one at a time and support it, shake the wheel side to side, while someone is under the front watching for a worn tie-rod end, loose or bad wheel bearing assembly, or a bad center link/drag link.
Take a rod and put it under the tire and lift up and down and watch for a bad lower or upper ball joint, look at it closely when lifting on the tire, the bottom ball joint will look like it's going to separate.

Need to get it checked first but reckon you may have a buckled wheel, or similar. Also check tyre doesn't have a dangerous bulge in it due to carcass failure.