K1 and K2 are the same, and sold by the dealer.
Here are some meaty threads to help:
K2 spring number for tranny 722.3 - Mercedes-Benz Forum
K1, K2 & B1 accumulator spring kits - Mercedes-Benz Forum
DIY Mercedes 722.3 722.4 722.5 Transmission K1 Piston Spring Repair Kit Install - Mercedes-Benz Forum
K1/K2 does not fix the problem. What i would do short of rebuilding the transmission. Is rebuild the valve body with new seals. mercedes does not sell these seals, but I would buy the $100 dollar tranny rebuild kit from rock-auto(it is by TransTech-American Company) as it contains ALL the seals for the entire transmission, but you are interested in all the little "dime-size" Teflon seals in the kit. One does not need to separate the valve body to expose the "balls" just remove the valve body(and you may not even need to remove the valve body, but just remove one valve at a time, and replace the seals one at a time), replace the large paper gasket(it is in the $100 dollar kit) replace the seals under plate. It worked for me. You can do the whole job in half a day or a day... You will need service literature for reference. I have it if you are interested. I cannot post it as it's too large to post here.
Best of luck,
Martin