A couple of pounds at most. Not heavy. Easy to install. We installed it and one side of the TV was lower. No problem...there are two screws on the back that you use to raise or lower each side to get it perfectly level on the wall. It took us some time to install it but only because it was the first time we'd done it. Now that we know how to do it the next one will only take about 10 to 15 minutes. Use a level to get the wall bracket level and you'll be fine. If it's your first time check out YouTube for easy to follow instructions. Hope this helped.
I do not believe that the vertical pieces are sold individually. You may be able to find them (if you are lucky) from a used seller, however I do not think that retail the pieces can be purchased individually. Contact the manufacturer for specific confirmation.
I had a situation where the house I bought already had the mount, but I could not find the serperate vertical parts. I thus had to purchase the whole set again.
The Box does include spacers as well as screws to fit most common manufactures. My TV actually had them already installed in the back of the TV, I've found that to be true for all of our TV's. Good luck.
Look up the hardware spec for the size and thread bolts in the manual that came with your TV or the Rocketfish unit and buy them at Home Depot. Manuals should also be on line.