Tell the repair guy you need it for your exams, to solder an external switch on the keyboard conector to power it on, pay him for the job that's been done, and get it back in your hands.
Until you're finished with your exams use an external keyboard.
I was once like you, poor student, decided to reinstall my system so i had everything neat for studying, one of the steps was upgrade the bios, well, the antivirus that came with the factory restore image blocked the update and bricked my new laptop! Since i am an electronics technician, and even had done hot-flashing in the past, i decided to fix it, turns out the flash was soldered, no problem, i had to revive old computers so i could flash the chip, then things went downhill, long story short it wouldnt boot anymore after soldering the new chip, i spent many many days and ended up having to buy a new motherboard, exausting my cash reserves, i can honestly say that that event f***d up my life, i failed that school year, and had to spend all my free time doing badly paid repairs for years after that (im in a poor country).
This will not take you 5 hours to learn and fix, you have probably already spent more than that with your current research and reading forums looking for a fix. a laptop membrane keyboard is unfixable/not worth fixing, in my gaming laptop the keyboard has gone bad twice and i've never ever spilled or eat anything on top of it.