Is my phone worth fixing?

Couldn't find my phone, went on Find my Iphone with my GF's phone, saw it was 20km away in a ditch. Tracked it down to where I'd pulled over to clean my windshield (big snowstorm), a few hours earlier. Must have fallen out when I opened the door, doh. . . Screen was crushed (probably drove over it when I pulled away), but the find the iphone worked as did 'playing a sound' using Find My Iphone. Back home now, I managed to turn the phone off using the top and home button. Before it turned off, it would vibrate each time the home button was pushed. Eventually it showed a vertical stripe pattern of purple and green and other colours. Got the screen off the phone, and although the inside is pretty dirty, it wasn't actually that wet and the case is fairly intact, though there are a few small dents on the back.

So I know warranty is useless, but is there any chance this phone's motherboard is intact? Could the colours and stripes showing on the screen just be the LCD itself being fried or is it a sign that the motherboard is fried? Playing the sound on 'Find my Iphone' worked a second time right before I turned it off. . .

Anyway, what would you all do in my shoes? Spend the 59.95 on a new screen and try it, or don't throw good money after bad and save up another $549 for a new phone? Should have gotten that extended warranty.

Thanks for any help you may have,

Farmer robin