newbie question

Looking into getting dtv but i have a couple questions about it. One is that i have alot of trees around the house but i used dishpointer app on the iphone and shows the sats. a little above the trees, if i order an the tech comes out will he be able to tell if its possible. If so what if it doesn't work out will i be able to have them uninstall the equipment and get my money back or im i stuck with it. I like the whole home dvr deal but the only draw back is it doesn't work with the tivo unit. Is it worth the cost because i only have 2 tvs so give me some of your advise. thanks