You can get a powertrax locker which is limited slip, for around $400 and maybe even cheaper. This friend of a friend is charging you too much. You can do it yourself, pretty easy and it will replace the damaged spiders in your dana 44.
As far as welded spiders go, if its a crappy weld and pcs of the weld fall off while driving it will grenade everything in the housing. So make sure everything is tight. Driving around on welded spiders is an advanture going around corners especially. Be very careful on wet roads.