Aye Simon it looks like I get to bone up on the Kings' English today
. Measure the depth of the old seal then drive the new one in to that depth and pack some vaseline around the spring on the back side so it wont pop out. Smear a light coat of your gasket cement on the housing ID where the seal will reside at, rather than coating the seal OD itself as it will get wiped off as it travels toward it's seat plus you dont want any on the bearing. Get the seal started straight w easy whacks then whack it in to the right depth w as few strokes as possible and have something circular on the seal as a driver that has an OD AT LEAST midway of the OD of the seal. Wrap the splines w a piece of brown grocery bag and when the splined end is inserted past the seal then pull the paper out so the splines do not contact your new seal. I'd set end play on the low side (.005") .010" max. As said clean/blowdry/repack the bearings. And I swear by taking off a holddown and a return spring and taking off a shoe and the horizontle ebrake lever for EASE of axle R&R (trust me on that one)