Dont quote me, but ive heard 9 grand that includes the drivetrain, as for the hood and stuff that would probably be all add on stuff.
your best bet would be to pick up the L if you can, upgrade the suspension, body, brakes etc, in effect prepare the car for a wrx drivetrain, then do the swap.
if you had an rs it would be more of a drop the wrx drivetrain in and go.
ask your self if you would spend more money updgrading an L to handle a WRX drivetrian, or would it be cheaper to find an RS to just plop the drivetrain in and pretty much be able to drive it out the door.
thats what I would look at if I where going to do it.