I can't tell you how many cabinets I have smashed over the years... Why build one when 1,000's are scrapped every year that could be perfectly re-purposed?
Some other things to consider:
Do you have a tilt?
Do you have a plunger?
Where are the flipper buttons, and speakers going to go?
How will you configure/start a game? (Wireless keyboard is a popular solution.)
What device are you going to use to connect the inputs like title, flipper buttons, and plunger actions? USB-ipac perhaps?
Those bare wood sides are going to be hell on your hands. What about side rails and a lockdown bar... You will need some way to attach that stuff... and if you buy new, it's not cheap.
There are so many 1000's of possibilities that you will need to provide some more info about what you want the final product to look like before anyone would probably be willing to help.
The only advice I have is don't try to reinvent the wheel. You can pretty much buy all the parts you need (besides possibly the cabinet itself) from 4 sites on the interweb. Companies specialize in building these and use "off the shelf" readily available parts in nearly every one I've seen.
Focus on what you have now. Find the biggest nerd you know and have him build the pc and get it running with a keyboard and mouse for starters. Install the emulator you want to run the games on, then check back here when you have that up and running.
This is less of a pinball task and more of a computer hardware building task.
