Yeah, if your windshield is cracked, it reduces your visibility, and could cause an accident - insurance would want that replaced quickly. At least call and ask them.
I've done it myself on a CJ, and it's not hard (I replaced the windshield frame). There is a trick to put a string in before the rubber, then once it's in place, pull the string out, seating the rubber correctly - at least that's how I remember it...