How to reset firmware?

I have a problem with my 2009 macbook pro (mbp5,5).
I ran a firmware update but it failed, and ever since i can't boot my MBP.
When i turn it on it beeps S-O-S in morse (3x3 beeps) which indicates a firmware update is in progress as described on the apple support site.

The apple support site mentions there is a firmware restoration CD available, but there is no version listed for my macbook model. I have tried several, but they did not work.
I also tried some key combo's like the PRAM reset, but it seems the macbook didn't respond to any (also the capslock led doesn't work).

I went to an apple store hoping they could fix my problem, but they didn't knew the problem and told me they could only replace my logic board with a new one. However i have no applecare warranty left, so this would cost me a lot of money.

Has anyone experienced the same problem and found a solution?
Or does anyone have any tips of things that could work?
Please be so kind to help me, you could save me an expensive repair!