Faulty PSU - repair or dont?

Hi there, I received PC from one of my collegues in work and he wants to sell it to me but I decided to test it first.
It turned out that the PSU doesent work. It is Corsair CX500. When I disassembled it I found that there was a screw inside the PSU chasis that probably fell down there somewhere from the other PC part above it and shortened something. However I cant smell anything burned and it doesent look like something is damaged.
Since I dont intend to buy that PC and keep it but instead I plan to resell it I wonder if I should send that PSU into service for repair (I have no idea how much it could cost) or if I should buy some cheap new one that is good enough for the system.
By the way the system specs are:
Athlon 760k
Gigabyte A88XM-DS2
2x4GB ADATA XPG DDR3
R9 270
1TB Seagate Barracuda
DVD Drive

I also need to test if all of these components work but I cant do that without working PSU. So far I know the GPU works.

Also if you could recommend me some cheap PSU if you think it is not worth to send that previous one for repair (it is no longer in warranty). Also I am from EU so prices may be different than in US.
Thanks in advance.

Faulty PSU - repair or dont?