please help with my Mac Pro issue

Hi -

I use a Mac Pro 5.1 2010 3.46GHz 12 Core - 96GB RAM - ATI 5870 - USB 3 - 1TB SSD

All the drive slots filled with music files as I write music with it.

It powered down a week ago when I moved a cloth over the back of it ( I think I stupidly pushed dust into the fan grill and wouldn't switch back on.

I took it to a local repair shop (North Manchester) and since then they have tried changing the power supply, and they have just changed the motherboard but despite the new motherboard showing signs of improvement (the fan switches on / the graphics card show signs of life) they still can't get anything to come up on the screen.

They have been really helpful but they aren't really Mac specialists and I would REALLY appreciate a Mac repair expert or similar advising me here.

Because my Mac is set up just how I want I'd really like to avoid having to migrate all my software etc into a new machine, re-installing everything - I'm aiming (if possible) to replace parts until it comes back on the way it used to.

What should I do next? Obviously these machines aren't horrifically expensive, If I get another machine is it possible to just stick all my drives in it and have it appear jsut like my old machine? Should I buy a new CPU (this hasn't been tried yet) and if so does it need to be exactly the same clock speed as my old one for there to be any hope of everything returning to normal?

Any advice appreciated from someone who has dealt with these before.

Thanks very much

Ben