Re:
You might be able to repair the threads using helicoils, or retap for the next size up bolt. The second option would probably require a bit of work to the brace too as the countersink for the bolt head will need to be enlarged. Not too big a job with the correct tools though.
As for servicing the forks, I guess you need to weigh up the costs. You may spend a bit of money on the ones you have to get them working properly, but at least you'll know the condition of them once it's done. You could spend a lump of cash on a better fork & still have to service it?