some help much needed for a wrangler novic.

alright well thanks in advance to anyone and everyone who can help me out on this. my younger brother just got a 06 wrangler x 4x4 4.0L... well i got a call yesterday(i live in another city) stating that he felt like his gears were stuck between neutral and drive, and that it wouldnt run... so after much searching and checking and thinking, he had it towed to his home. the gentleman who towed his jeep for him managed to crawl under it and fiddle with whatever was broken long enough to get it to drove into the driveway. i was told by way of relay that the issue was a "broken gearbox". and that its plastic and happens all the time. all i could find online is the broken shifter linkage. i found a link that says that a simple bold and nut with washer combo will fix this issue almost permanently. can anyone please tell me if they have dealt with this before or if this is the correct fix for it? im trying to save me mother the time and money of a shop fixing and charging her for this...