Jesus H. Count of Monte Cristo... I think you've managed to touch upon the dark side of laptop servicing... I still think there's sweet stuff inside your laptop - which is what attracted the ants.
What speed is your EVO and how large is the LCD display? If it is around 1GHz, then it might be cheaper to buy a used EVO system off of a reputable eBay vendor, or anywhere else, for that matter, stick your hard drive into it, then put your original system up on eBay for sale as parts - you'll be surprised at how much money it'll fetch...
I would probably not go and bid on a motherboard thinking that I'm gonna get working parts out of it: (1) there are many different EVO models and they aren't interchangable with one another, and (2) these parts are manufacturered onto the motherboards and things like connectors are damn near impossible to remove. The thing that pisses me off is that your system has already been gone thru by three incredibly incompetent "technicians" - I mean, these guys might as well have been auto mechanics equipped with crowbars - and who knows what kind of damage they've done to your laptop while they were "working on it." I have to tell you that when I performed repairs, approximately half of the work I did was to fix damages that were caused by other incompetent techs - and these were the absolute worst kinds of damages inflicted on top of the original hardware failure.
It's like a guy is dying - the 1st doctor came and carved out his liver, which didn't fix the problem; the 2nd doctor came around and removed his head and then took his head apart to find problems inside. So now the guy is deader than dead. Well, if you take the body + the liver + the head to a 3rd and real doctor, how is he supposed to know how the man should've died, or lived? That, unfortunately, is the scenario that you ran into...
So... if you spend $500 on a used, replacment EVO system, and you eBay yours for $250, then I would think it's a fair bet. You'll put all these "technicians" out of business, of course, but that's fine with me.