Hardware replacement to fix not-working MacBook keys
Most repairs in retail stores are for less than 5 days - and more than half the repairs are done in less than 24 hours. 

There are some bad signs in the symptoms you mention. Sleep sensor failing is often liquid damage. Keyboard keys failing is also often liquid damage. Even if it's not liquid damage, the logic board or keyboard and some other parts would need to be exchanged and the keyboard is part of the unibody frame, so basically it's like taking a car in for a new frame. All the old seats, engine, power train, etc… get hand removed, inspected and re-assembled in the new chassis. It's not that bad, but it's a lot more time consuming than just putting in a fan or a battery or hard drive in. Those take 20 minutes tops.

So, as you mention - finish your work, keep good backups and then send it in knowing it's likely to be $150 to $320 to fix (in the USA presumably) and if there is liquid, you should probably sell it for parts, since the repair cost will jump to $800 or so.