If it is your crankshaft seal, you will probably have to take quite a bit of stuff apart to replace it. But I haven't heard of anybody having to replace their crankshaft seal on a Titan yet. Are you sure that it is the crankshaft seal that is leaking? Other common leaks in that area are things like a tranny fluid leaks coming from the hoses going to and from the radiator (or from the radiator itself) or even an oil cooler leak. Sometimes people have also had their front dif puke gear oil all over their engine bay out of the overflow which is located next to the airbox. But if you are having problems identifying whether the leak is coming from the main seal or not, chances are that a main seal replacement wouldn't be a repair you would tackle yourself anyway, so I would just take it to a shop.