Headers?
#4
Helping the engine breathe easier will relieve a little stress on the mpg area. As to putting more wear on the transmission, probably not. With the engine able to output a bit more stored power easier, it might "use" the transmission a bit more but as to putting wear on it, just keep it well lubed and all the suspension fittings greased and you should be fine.
#6
http://www.stylintrucks.com/Articles...0/article.aspx
might give you an idea time wise and how hard
might give you an idea time wise and how hard
#7