Should be easy, take out the old cylinder and replace it with the new keyed one. Shouldn’t even have to disconnect the battery, unless the instructions tell you to do so.

That beep is turned on or off in the mic set up menu, I believe all smartphones, pads have this feature. Hope this helps.

(1) Check speaker sound balance, might be turned all the way to the right or left. (2) Use an ohm meter and check continuity on the wires, might be broken internally. If you don’t have an ohm meter, then use the other set of wires that proved to work the “good” speaker and now check the non-functioning speaker on the same channel that made sound.