Being a HP model I'll assume you have the newer hydraulic tensioner. Seems to me all the K13's do. Anyway all it really needs is this O-ring kit:
11 31 7 705 460 SET: O-RING SET 1 $13.98
And then you will be good for another three years. You will need a box end Torx for the bolts and it is a bit fiddly to get out and back in but remember to tighten the bolts down evenly so nothing binds.
Mount Vernon, WA.
tire guy, I'll mount your tires.