First off, I hope your home owner's insurance is up to date if you intend to remove the tree yourself. If any of it crashes onto the house, will you be covered? Check w/your insurance company.
As far as the root problem, you need to be sure you kill the root once the tree is removed. There are a number of ways such as grinding, rotting, taring, etc., etc.. You can search the WEB for options. (If you're unsuccessful, e-mail me directly.) You may want to dig up around the foundation to get at the root that's up against it. If it's under your porch, well, take your time and go for it. You shouldn't have to go down too far. Do have some extra dirt around to build up some POSITIVE slope AWAY from your foundation. Over time, the ground where the root is may settle and you want to be one step ahead.