Whereabouts
You may become a Cyborg, as well as buy and equip weapons/attachments/etc. etc. etc. at the Junk Shop but the actual process will take place at the Underground Garage.
Requirements
You must have a minimum experience amount of 200,000 in order to survive the process of getting cybernetic parts as well as the brutal beating that the mechanics put you through and the cost of the process is 100,000 Beli.
Cyborg Battle Info
Cyborgs fight just like any other human except that they use special weapons and items run by cola power. While in a fight, cyborgs are required to keep track of how much cola they have left in their fridge. If they run down to a lower number, they are allowed to refil all their cola taking up one post to do so if they have any extra cola. Cola can only be refilled once during a fight though.
Other
Once you become a Cyborg there is no going back. You cannot get the parts extracted like you can for a Devil Fruit. This is something that will follow you through the whole guild.
However, you may have your Class of Cyborg changed a maximum of three times before the trauma overloads one's brain and heart and shuts it down completely.
*Note: You may not be a Cyborg and have a Cursed Fruit at the same time.