Your tractor must either have an SOS transmission or a crash box that does not have Independent PTO as they were the only 3 cylinder 4000s that used the side pump and external lines.
It should not be hard to braze either of those lines though you may have to drain the oil out of the rear end to get it out of the lines before brazing if you do it in place.
There is a 3 bolt flange on the pump and 4 bolt on the rear end. Easy to remove.
Nothing behind them to worry about except I would replace the Orings if you remove it.
I have a good set of lines from a 4000 here if you find you can not repair the one you have.