Nikkor AF 18-135 lens won't retract fully

The sensor on the D80 is smaller than a piece of 35mm film. This means the camera will only use the center portion of the image cast by the lens. This reduces the angle of view, effectively increasing the focal length. The 35-70mm will give you an angle of view similar to a 52-105mm lens on a film camera. Likewise the 70-210mm lens will give you an angle of view similar to a 105-315mm lens.

If you mean the AI-S Zoom-Nikkor 35-135mm f/3.5-4.5, you can download the manual here.

That lens will work with the D3100, except for the autofocusing. In order to autofocus with the D3100, you need AF-S lenses, such as the AF-S VR Zoom-NIKKOR 70-300mm f/4.5-5.6G IF-ED or the
AF-S DX NIKKOR 55-300mm f/4.5-5.6G ED VR.

Pull the lens all the way IN (i.e. zoom to 70mm) then press the MACRO LOCK, and then adjust focus using the macro ring.

No. The lens will work with every Nikon film or digital SLR made in the past three decades or so, though of course the autofocus won't work on older cameras that don't support AF.

Yes. The lens is fully compatible and functional on both the D700 and the D3.

i was not able to find a manual - this review may help http://www.kenrockwell.com/nikon/3570.htm
The lens consists of

1. Zoom
2. Focus
3. Aperture
4. Macro

1) Zoom - this is by push pull - so you push the lens out to wide angle 2) To switch to manual focus - will need to be done on the camera and then you can use the front control ring to focus - 4) also you can use the button to switch to macro mode - BUT only with the Zoom at 35mm - lens fully extended 3) You have an aperture range of 2.8 - 22 this varies the amount of light allowed into the lens - 2.8 is the most light - F4 to F5.6 to F8 - each change halfs the light allowed in - so changing from F4 to F5.6 half the light

Try sending it to PhotoTech Repair Service in NYC. They are Nikon authorized, and can do the repair under warranty if you still have it. Also if you join they're facebook page, they will give you a 10% discount.
Here is the facebook page link, it has everything you need to send it in.
http://www.facebook.com/pages/New-York-NY/PhotoTech-Repair-Service-Inc/102527215194

Blades are dirty.

Test by setting up for 1" shoot and look into the lens.
If blades close late then they are in need of an PM.

I repairs & serivices cameras, flashes, lens and studio lighting.

[email protected]

Don't force it.
Did you get dust or dirt in it?
The only solution is to bring it in for service or send it to Nikon if it is a USA model.
Nikon USA will NOT repair any gray market items.