Will this lens fit on my Nikon D3000?

Http://www.bhphotovideo.com/c/product/207359-GREY/Nikon_1928_AF_Zoom_Nikkor_70_300mm.html
I know the D3000 doesn't have AF with some of the lenses. Will I have to manually focus this? If so, is it hard at all? I know you have to turn the focus ring on the lens. But before I buy this I want to make sure that it will fit with the D3000

That lens will fit and meter, but you'll have to autofocus it on your D3000 and any other Nikon entry level dslr.
The alternatives would be the Nikon 70-300mm AF-S VR or the new 55-300mm AF-S VR.
Here's a Wikipedia page that lists all compatible autofocus lenses for your camera.
http://en.wikipedia.org/...cus_motors

Yup, you'll have to focus manually (just turn the ring).In your shoes, I'd look at the 55-200mm AF-S VR Nikkor, which has been designed to fit your camera and complement the 18-55mm you already have.