I'm in the middle of my first build, so I'm certainly no expert. However, I did a little homework before I ordered everything.
On the lowers, it doesn't seem that anyone has a real yes or no answer to any of these. I went with Mega Machine Shop. There is a thread in EE for them. I think they look great, and the machining seems to be top notch with much attention to detail. Stag seems to be another very popular choice, but there are certainly others out there.
I shopped around with a few different places to get my lower parts kit. It seemed many were not impressed with DPMS and as of later, some didn't like RRA, so I went with CMT. Many reported them to have a good rep. I'm expecting it will work fine.
As for tools needed. There seems to be many different interpretations of "need." Check the tacked thread that has the instructions for building an AR. It should give you a good idea of what you are gonna want or "need."
Gundraw