There is no need to book a time slot, just pop into the store during business hours, the store location and opening hours can be found here.
Yes. It’s not that hard to replace keyboards on the majority of low- to mid-range laptop models. However, the job is finicky and requires a steady hand. You must be particularly careful not to sever the data cable connection joining the keyboard to the laptop screen. In most laptops, this connection is quite tight, and easy to break if you don’t know what you are doing.
Usually it takes approximately two working days to complete.