If you've rebuilt gearboxes before the cost is mainly in getting the bearings. There's also a lock nut at the back of the main shaft that can either be replaced or machined slightly to get a new lock in section. Last time I got bearings it was about $100, but that was a few years ago. Any diff & transmission place should not have any problems, either, unless they're incompetent. With the broken shifter pin, take those along & see if you can get some stronger pins. I've broken a few over the years & my friend who rebuilds them for me always puts something stronger in.