While it's certainly possible and potentially very rewarding I'd spend some quality time planning out how you'd go about this. Put together a list of everything you can think of to get an idea of what you'll need, where you're likely to find it and what it might cost. There will be plenty of elusive details that need to be sussed out. If you plan to build this out of donor EM games for example figure out if there are any parts (e.g. stepper contact discs and wipers, backbox panel, wide drop target banks) that were only used on this game or on just a few others. Also figure out what skills you'll need (reading schematics, programming, trouble shooting, woodworking, painting, etc.) and how much of that you can do.

It might be tempting to scoop up some donor games and get started but a little planning ahead of time is free and might save a bunch of heart ache later on.

/Mark