For the rings (depending on how brittle) you can usually get the thumbs in there, spread it and pop them off, just go slow. The new rings will most likely be a lot more pliable and easier to spread. Seems to be the preferred method around here, if for no other reason than it's free ;P
If you want, you can also get a ring tool, they're just a couple bucks, saves the thumbs and can really make it a lot easier.
Peanut oil (or butter like RAF said) will do wonders on old plastic parts. There is a thread around here with some examples, really looks sharp, and it's pretty cheap.
Are you going to reuse your steering bearings? If not you can obviously be a bit more aggressive. A lot of guys use a bronze drift, and just tap side to side till it slides off. I wasn't reusing mine, so I just took an old eninge bold and used that, eventually it pops right off.
Things are sure looking good!