This looks to use some standard size laptop HDD. Maybe a new HDD and fresh OS X install would be worth a try. A new motherboard is certainly more than most folk will invest in an older model.
Figure 50 bucks for a run of the mill 500GB Laptop HDD if you DIY. Good luck.
I have a MacBook Pro from 2011, recently it fell to the ground, the screen went blue, it started to make a very acute noise for a long time. Then it finally shut down. When I started the computer again it was very very slow, it's dragging itself. I can't do more than one thing at a time.
The worse part is so far two programs don't work, Photoshop and Bridge, I try to open but it crashes and I get a huge error report, that i can't paste it here because its too big. I think it has something to do with hardware because of the fall, maybe its the processor or the RAM that is broken...
But here are some parts that seems strange to me:
VM Region Summary:
ReadOnly portion of Libraries: Total=378.5M resident=166.2M(44%) swapped_out_or_unallocated=212.2M(56%)
Writable regions: Total=435.4M written=104.1M(24%) resident=197.2M(45%) swapped_out=0K(0%) unallocated=238.1M(55%)
REGION TYPE VIRTUAL
ATS (font support) 32.1M
ATS (font support) (reserved) 8K reserved VM address space (unallocated)
Activity Tracing 2048K
CG backing stores 8556K
CG image 460K
CG shared images 656K
CoreAnimation (reserved) 20K reserved VM address space (unallocated)