Replace battery on MacBook Pro M2

It's pretty simple. Battery replacement will be available for fee. One pretty much all of the latest MacBook Pro models, the method of replacement is to swap out the entire top case with a service replacement top case that could be new or perhaps reconditioned, but with a new battery.

There are caveats though. They will list a battery replacement price (if done through Apple) and they expect a good condition top case, although normal wear might be OK. The exchanged top case has value to Apple to recondition into a new service replacement, and some might not be in good enough condition to reuse. If it's not in good enough shape, they would probably advise that they will do the service at a top case replacement price, which would be similar to replacing a completely damaged keyboard or heavily dented top case. The standards for allowed wear aren't all that clear though. I would expect a few worn keys might be fine since they can be replaced, but if the entire keyboard is worn down or there's heavy dents to the case, then that's another matter.

For some of the newer models, Apple has a self-service repair option, although they can't really account for the user performing a service incorrectly. For Mac batteries, I haven't seen anything other than complete top cases from Apple's self-service sales partner. They will offer a small exchange credit though, but the overall price I saw was more than having Apple perform a battery service. The battery itself is typically glued into the top case and the process of removing spent batteries and reconditioning the top cases are done at centralized repair facilities.

Just to clarify, battery replacements can be made for Macs, and that is independent of whether or not you paid for AppleCare. It's just a repair service for a price. And even if you got AppleCare, that expires, and the cost of replacing a battery would be the same.

If you did have AppleCare (or perhaps AppleCare+ which may not be available where you're located) there might be an extended warranty on the battery that would allow for replacement if it doesn't meet Apple's design specifications. That's assumed to be the battery level dropping below the rated 80% new battery capacity within the AppleCare period and before it has accumulated 1000 cycles.

The specifics for Apple devices are given on the Apple.com website, in the printed literature and all the regular places as specified by whatever governing bodies there might be

But, it's the responsibility of the buyer to understand what's being bough and its Terms and Conditions.