Having a second camera is really a good idea. I kept my D3000 after I purchased the D7000. I carry it just about everywhere. It is small, light, and can fit in my purse, along with my knitting. Yes, I use a very, very large purse. When I was still using film, I always had at least 2 camera bodies and carried one with me no matter where I went. I started that habit in college.
I do not know much about the D70 but it should definitely give you better images than a P&S.
I would get it if it's in good condition, and as Jack said, has the charger, etc. with it. As a couple of people have said, it's worth it for the lens, alone.