Don't know too much about them but a friend who does mobile diagnostics says the power shift box is very troublesome and expensive to repair.
If there's swarf been through it it won't have done it any favours so if it's still going ok then it might be an idea to get rid now.
If it's a wet clutch I.e in the gearbox then possibly it's failure has caused the swarf but metal floating around won't help it any.
What does a second hand box cost from a damaged car?