The easiest way is to pay a shop - alternatively there's probably instructions in the 348/355 section
As a general rule of thumb, it's best to hook up a battery charger/tender before disconnecting the battery to keep any computer chips powered-up. Disconnect the negative terminal first to prevent the positive terminal from sparking when it's disconnected. With the new battery, connect the negative terminal last. Make sure there is no corrosion on the inside of both terminals. Don't over tighten the battery hold down.
There is no easy way to change a battery on a 348. Just be aware there are different locations depending on the year of manufacture. Is yours forward of the front right hand wheel arch, requiring a wheel removal?
