EGT on that little thing shouldn't run much above 900 in the pipe. 900-1000 is fairly common. More discoloration in the bend is fairly common because the blast is directed at it and focused on that spot. It was always a common thing to see Ford's that were turned up... blow the top bend out of their mufflers.
I've brazed diesel exhaust pipes before. Generally, if the high temp paint on the pipe hasn't been burned off the brass will be fine... but in this case... I'd say the pipe is already thin from the inside. It probably wasn't much more than 16 ga anyhow. It's just thankless trying to fix that. One thing to play with it; quite another to charge someone money for it.