Pixhawk 4 clues to how it works

I have a hex drone DJI 550 flamewheel with a naza flight controller the dji software will not talk to windows 10 so I am thinking of changing to Pixhawk 4 a/ how hard is it to work B/ I see the one you sell is over 400 but on ebay from australian sellers they are about 170 whats the difference I see yours may include power management board and thirs may not any clues .I am not dumb but i am not super tech savvy either