The north depower line is designed to look worn and tatty when it needs replacing.
By the look of the corroded elements the bar has not been regularly rinsed after use.
It is a simple replacement with 5mm amsteel dyneema, most kite stores should stock it, a bit of practice splicing to make the loop and as said before the most difficult part is re-feeding through the velcro hoody and hopper.
North sell the kit for about $35 and this takes out the hassle of splicing etc.
We get customers in who are quite happy to pay an additional $20 to fit a $20 replacement valve.
Some people just want to get back out on the water with a minimum of hassle, and don't mind paying for it.
With all basic repairs and maintenance, kites shops would rather just show you how to do it yourself and sell you the spare parts, rather than actually doing it for you.
But if you want you gear to last longer a couple of tips:-
1. Rinse your bar and lines, harness and board in fresh water after each session and dry in the shade, and you'll double the life of your equipment.
2. Check your seams for dropped or missing stitches when you pack the kite away, this makes it stay as $5, 20 second restitch rather than a 2 day $100 repair.
3. Check your canopy for small tears and abrasions and get them patched and sewn before they become full-on LE to TE rips.
4. If it looks like it needs replacing then, get it done before your next session not after a 2km swim in