It's a very good idea to have some sort of a spring compressor for disassembly and reassembly. If your rifle is currently shooting 17 foot pounds then you definitely have a full power spring and the spring will have pre compression on it.. could be as much as 2+ inches when you finally get the end cap off.
The end cap of the HW80 unscrews and can be a little difficult to get started to unscrew, because it screwed in very tightly to line up the scope dovetail. You may need to use a crescent wrench wrapped in a cloth and inserted into the end cap and then tap that with a hammer to loosen it so you can unscrew it.
Putting it back together could be a challenge to compress the spring and screw in the end cap again. You have to go very slow and make sure everything is lined up to avoid cross threading of the big steel end cap.
I have taken my HW80 apart a few times and it currently has maccari power kit in it which gives me around 20 ft lbs. However, due to spring pre tension, it's a challenge to reassemble even with my over built spring compressor built on a 2X 10 board as the bed with a bench vice as the pusher.
I'm not sure what reassembly will be like with the hw80 soft tune kit from macari, but I would bet the spring is shorter and you won't have as much difficulty reassembling it..
There are videos on YouTube on the tear down and reassembly of the HW80, you just have to be mindful that some of them will be for the low power Europe versions and the spring pretension inside will be lower than on your full power spring of your 17 foot pound rifle.
There's lots of other guys here with a lot more knowledge and skills than me, so if I missed something I'm sure someone on here can help you.
Almost 2 years ago, I was reassembling an older hw50 which has the same style construction as the hw80 and I nearly ruined it by cross threading the end cap. The guys on here helped me figure it out and I got it put back together. Which is why I sent this rambling message, just thought I could give back a little bit.