I was wondering if anyone knows why I would be smelling antifreeze while the defrost is running? There is also some kind of oily film on the windows. I just noticed this last night and then while driving it this morning there was like smoke or something coming through the vents.

Souds like the heater core is leaking!

thanks I will have to check that out.

You will probably find that your radiator is a little low too.

You will probably find that your radiator is a little low too.
Mine does that too when my anti freeze is low.

Probably the heater core is leaking.
I did mine last year, and it is a pretty ugly job. Essentialy the whole dash has to come out at least far enough to work behind where the passenger side airbag is up against the firewall. The dealer wanted 10 hours labor at $87.50 per hour. I did it in about 7 hours and I feel I'm a pretty decent wrench turner. There is a document posted somewhere here or at www.f150online.com that describes the procedure in good detail on how to do it. The part is ~~ $50 at NAPA.
I have the document in MS Word format. If you drop me a PM with an e-mail address, I'll forward it to you. Also the heater hoses require a special tool to remove them. I bought one for $30 at a tool specialty house. Some people just cut the aluminum lines off the old core and get the hoses off once they are out of the truck.

I would be willing to bet its the heater core also. If you need to replace it make sure you use a more expensive higher quality one.