yarquint,
I don't think the people at HD will make the cuts with the precision you need. Not only do the cuts have to be square, but you need multiple pieces to have the exact same dimensions. All of your posts must be the exact same length for the top to be level. All of your top rails must be the exact same length for the stand to come out square.
There are some cool tricks you can do, though. For example, when I needed to cut several 2x4s to the same length for my stand, I would clamp 4 together and make a single cut on the miter saw...that pretty much guarantees 4 identical pieces of wood.
Remember, no one at HD has a vested interest in how your project turns out. If you're reasonably competent and handy you will do a better job (this is good advice to live by). You may want to consider renting/borrowing a chop/miter saw, or you can even buy a cheap one for $100.