will 2 door 2002 ls bumpers and side skirts be a bolt on fit to a 1998 4 door base model cavalier? will I have to do some fitting to make the 2 dr side skirts fit on my 4 dr base model? if anyone has experience changing these bumpers out or anything please help me, looking to swap my front bumper, rear bumper, and side skirts to the 2002 ls sport bumpers and skirts.

Rear bumper will swap right on. Side skirts will be fine just a little bit of work drilling hole into the rocker panels for the weird mounting clips (unless you already have side skirts on there)

As for the Front bumper the 95-99 style headlights are different than the 00-02 style headlights, so the 02 bumper will "fit" but there will be about a inch gap underneath the headlights.
This gap is unattractive.
(Because the 00-02 Headlights are deeper than the 99 style)