At 80k.... I would change the belt with a quality one (If not Mitsubishi, then Continental etc). No cheap belts... it breaks, you need an engine. You don't want to save $40 and end up in worse shape. Then inspect the rest and replace as needed (if).
I would be extremely cautious about that kit as the pricing is pretty low. Just keeping in mind the water pump is $220 (Retail of course) and the hydraulic tensioner $160... they would likely be selling at a loss to include all those other items too. It is possible, but I would be suspicious if it is coming from any source other than one with "Mitsubishi" in the company name somewhere :)
Otherwise I would inspect and replace as needed with regard to pulleys, water pump and cam seals. At 80k it is unlikely you will need any (nor need them by next interval either most likely).
If you want to replace the pulleys or hydraulic tensioner you can, but honestly I would feel more comfortable with an 80k mile factory one on there than an aftermarket one with regard to the hydraulic tensioner. The pulleys seem to be OK from just about any brand.
Do not use an aftermarket water pump. No exceptions on this one, they are all junk. Even major brand ones like Delco etc, they are all junk. There is a reason the Mitsubishi ones cost $220 and the aftermarket ones cost $50. Mitsubishi ones last 200-400k miles if the coolant is serviced even somewhat regularly. Aftermarket ones have been known to fail inside of 10k miles in some cases. These get towed in somewhat regularly with seized up water pumps that were just put on 6-12 months before... I won't even install them without guarantee for customers any more as I've seen too many fail. I would sooner lose the timing belt job than put even a "good brand" aftermarket pump on.
A similar story goes with the front seals.... factory only. Otherwise you are going to do it twice. For some reason the aftermarket cam seals are terrible fitting no matter where they come from. I can always tell when someone used them before trying to fix a leak then bring it to me, because the aftermarket ones you can gently pull right out, they just don't seal right. The correct fitment should be stupid tight.
And again on that one at 80k you probably won't need them anyway. If it were the older 3.0L then definitely, but the 3.8L will regularly see 150-200k on these seals if it was never run hot. Its your call on that one, but if you opt to do them regardless of leaking, be sure to get factory seals so you only have to do it once.