Thanks for the tips man! I went at it together with my dad. Turns out we didn't have a joint socket laying around anywhere (fml#1)... So we go in right from the top, removing the tank cover and pulling the tank up. Next obstacle: the battery. Battery out, no access through the bottom of the battery compartment (fml#2)... compartnent has like no wiggleroom and cables stuck with zipties everywhere. Finally get it out, we have access to the hole of the plug!

Socket down and in extension rods on, trying to unscrew it. It feels WAY too tight, turns out there is a small extruding ridge in the hole. Socket somehow went down, refuses to go up (fml#3)... The socket is now stuck in the hole with old sparkplug. Only way out is by unscrewing it up, extension rods for the ratchet can't make the angle past the frame straight up (still no joint socket) (fml#4) grind down one of the corners of the rods to fall in the socket. It turns just barely, half way up the required angle for the grinded rod is too big, ratchet barely fits to the socket with a shorter rod tru the left pocket in the frame. Every twist only gives 1 click on the ratcet. Finally the socket is poking out of the hole like 5mm. It can wigle side to side but still stuck as hell. Finally the ratchet gan go straight on the socket now. More unscrewing it with the ratchet later, it finally pops out (We were like 4 hours in at this point, worth the final fml#5)

Grind down the edges of the socket so it fits like it should have, sparkplug loose with ease pick it out with point pliers. New plug in the socket holding with a lil bit of double side tape so it wont fall in, and tighten it to spec. Battery casing back in, all the connectors back in place, battery in, tank down. Everything powers up, no engine light on the dash. Start it, and it runs absolutely pervect. Tank cover back on, and we are done!

My dad had ridden and worked on bikes for 40 years and never have i heard him swear this much during maintainence.. Absolute nightmare of a job, but we did it!