I'm also looking for an upper to complete my lower right now. I finished my lower about 2 months ago, and just haven't found the upper I wanted in stock. Now I wish I was a bit less picky...haha
As for time and tools. 1 hour to put together my first lower, which was taking my time, and the only "special tool" needed are punches to put the roll pins and such into place. So basically nothing special and pretty simple.
I have not done one yet. How much time do you have in it ? Did you have to have any special tool.