Is the Tamron AF 70-300mm TELE-MACRO a good lens?

I found a secondhand one for $100. (No, I can't afford a new lens)
Is $100 too much or is it a good deal?
I read that it has to extend to 180mm before you can use the macro mode. How hard will that be? I usually do macro 1 inch or less away. How hard will the transition be?
I have a Nikon DX camera, will this lens then be a 105-450mm? (Not sure if I did the math right)
Can it auto focus on the D3100? The D3100 doesn't have a auto focus motor.

Junk. Save your money for a little longer and get a Nikon 55-200 VR.

At 1 inch away, you will most probably need a 50mm macro. That 70-300mm will do macro at around 4 feet at the closest.

I don't believe this lens will work that great as a macro. They advertise them as that, but in my opinion they don't come close to a macro lens.

Contrary to manufacturers claims, zoom lenses are not macro lenses. They at best are closeup, as they can't achieve a 1:1 magnification, which classifies a lens as a true macro.

The only way to get good macro is to buy a true prime macro lens.

Tamron has been making this lens for quite a few years now. Only in 2009 they added the motor the D3100 needs.

IT's not a bad lens considering it costs next to nothing. MAcro.well. With practice you can do some pseudo macro shots. The fact that it only starts after 200mm does mean you'll be working from a significant distance which is not easy