Regarding getting it welded before it breaks, I looked into this and here's what I found:
A) If you are removing your tranny to get to the LSD it's silly not to do the clutch. If you are doing the clutch then you need to have your flywheel replaced or lathed (resurfaced). $ + more $ + more $ = no $
B) There is a rediculous amount of work involved, and if you are not a mechanic I don't recommend this job as a d.i.y.'er. Plus there is a huge benefit to a shop owning liability if the job isn't done correctly.
C) I asked around at many of my local shops (city of 200K+ ppl), and the highest profile transmission shop in town *refused* to do the job. This is because they couldn't do the welding, so this requires them to disassemble it, me to clean it meticulously and deliver it to another place for the welding, wait 2-3 days until I get it back, and then bring it back to the first shop for reassembly. They didn't want the "other shop" variable to botch their work so they just said "we don't want the liability."
The shop that finally did agree to doing it also did not do tig welding. They were going to charge me $780 + fluids and parts (gaskets, etc)...before tax. Then add another $150 for the resurfacing of the flywheel and tig weld on LSD together, and that's nearly a $1K job.
HOWEVER, if I were to give them an already welded new replacement LSD then the labor drops by about $350-$400 and the first shop would then take on the job.
When I looked at the cost of this plus the 4-5 days the car would be out of commission compared to the cost of just swapping it with a pre-welded OEM LSD it was pretty clear the latter was the choice to make.
You decide, but I don't think my experience is going to be extremely unique.