How old is this system? Even if it IS the motherboard, if you could replace with the same model (and preferably same revision of the hardware), there would really be nothing to do but put your OS drive back in (assuming it was not damaged), put your data drives back in, and carry on.  While it's not always a great case, Windows has even gotten better in most recent revisions at dealing with hardware like a new motherboard with the same Windows install, where it used to be a complete mess.
 
I don't really recommend the route of just putting your drive in dissimilar hardware, but you might at least be able to get a system up to get settings, serials, etc.
 
If you have to replace just a video card or something, that should be no big deal.  As above, if you can get the same model of MB to replace with, you should be able to just put it in and move along.
 
FWIW: I do this for a living.  Not really for DAW systems, but for Small Business PCs and servers.  As mentioned above, a vague answer and no remedy other than a wiped system is not a great answer.  In the case of a simple business system, we rarely do a lot of troubleshooting because they are so inexpensive to replace and in the case of a reinstall, it's generally cheaper for the customer to have it just wiped and rebuilt, but in the case of a custom system like this, we would definitely look a little deeper before just writing it off. 

If you have a usb windows 10 recovery thumb drive you can try this... worked twice for me.
 
Put the old disk drive in a new machine along with the recovery thumb. Boot to the recovery drive. Do a restore of the old drive saving everything and the recovery drive will get everything working for you including your programs in the new machine. Pretty simple. The thumb seems to see all the new hardware and include it with your programs. 
 
From your description your drive wasn't injured at all, just the tv or whatever. I didn't read everything so might be mistaken. 
 
If you don't have a recovery thumb borrow someone else's. 
 
John

If you have a usb windows 10 recovery thumb drive you can try this... worked twice for me.
 
Put the old disk drive in a new machine along with the recovery thumb. Boot to the recovery drive. Do a restore of the old drive saving everything and the recovery drive will get everything working for you including your programs in the new machine. Pretty simple. The thumb seems to see all the new hardware and include it with your programs. 
 
From your description your drive wasn't injured at all, just the tv or whatever. I didn't read everything so might be mistaken. 
 
If you don't have a recovery thumb borrow someone else's. 
 
John

Thanks for the help guys, I have sent the pc to the repair place, will be a few days, they will try everything to get me back up and running with the least amount of inconvenience so fingers crossed it works out in the end, All my work is ok and worst case scenario is a fresh install of all my programs and plugins.
Thanks again,
Andrew

Still seems odd that they would even suggest that all the applications and OS would need to be re-installed.
 
I lost a motherboard a few years ago.  I decided to upgrade my processor at the time so I installed new (and different) motherboard, CPU and memory.  I connected my system drive and projects drive to the MB and after some configuration, it booted right up.  Your repair seems much less intrusive, unless there was damage to the drive.

88% of the PC repair shops out there have not advanced beond Xp 32 bit systems. 
You get the job if you can look the part and answer 2 questions correctly. 
What does RAM mean?
What is a mouse? 

I had that happen last year, when my PC BSOD'd.
I had no problems reinstalling anything, and it was very simple to unregister the old installations. This type of things happen often, the vendors are used to it. And Cakewalk makes it very simple by having all the download links in one place.
I actually appreciated having to reinstall everything, it gave me a chance to NOT install all the things I never use.