How To Utilize A Phono Preamp Board As Stand Alone

If you're talking about cannibalizing an old unit, just rip out the regulated power supply board with it and the transformer too. That's all the power supply you need. Of course there are other options... A small toroidal can be easily obtained with the required secondary, and you can build a regulated supply with printed circuit boards from diyaudiostore.com. 

kosst is correct, that is about all there is to it.   Of course, you will need a chassis to put it in and all that goes with it.  

So...no comment on using a Walmart. 
And for the ground, I'm assuming there must be a frame it can be attached to ... that's an assumption I really don't know.