Well obviously you know the tranny clutch and flywheel need to be removed. I have installed them with just a lot of patirnce and a hammer with a wooden block. The best way to do it is to have something that fits the size of the seal and tap it in lightly. Dont ever force it. If you get it going in straight it will have some resistance but will move in with every hit.
Go easy and use patience other wise you will be redoing it in a couple of months. I think Autozone might have an iostallation tool you can "borrow"