Here’s a link for parts, LINK you may be able to source them locally for less, I would check the bargin caves at Cabela’s. Graph wise i think you can expect it to be a good quality graph, IIRC they weren’t cheap when new either, I’d pretty much expect it to be as good as the current units.
For me a graph isn’t a big deal when I’m running it up front, really I wouldn’t be unhappy running either upfront, pretty much a personal preference, the vex is probably a bit faster then the graph, if it were important to use to get instant feedback say you were jig fishing, but if you turn the ping speed all the way up amd the graph speed all the way up, it’s probably not far behind. The vex may also be easier to see in all lighting conditions, versus the graph. Personally I’d lean towards the vex myself. 
