Hi there,
had a similiar issue with my MBP late 2011 -black screen , no booting, ... .
I sent it to the those LRZ(Laptop-Reparatur-Zentrum Thüringen).
They checked it for free and told me my GPU has to be replaced and that it is possible.
They made an offer to do so for nearly 280€ including tests and a 12 month warranty on their work and 24 month warranty on hardware they built in.
My Computer works just fine since then (July 2017).
Can´t say yet what happens after the given time of warranty but so far i am super happy and can only recommend those ppl.
Best,
Giorgo