I would drop the bottom ball joint which should allow the shaft to slide out without needing to remove from the hub. Oil seal is easily prised out and then gently tap the new one in place ensuring it goes in squarely (and the correct way round).
The drivers side is a little more involved as there is the middle bearing that has to come out of it's housing as well. A Haymes manual will explain how it's done. Well worth reading before deciding wether it is something you are comfortable tackling. You will also need to top up the gearbox as you have already lost some oil and more will leak out while doing the job so having a try to catch the oil is a good idea as well.