I would say to verify that the axle face (where the wheel is clamped too with your lug nuts) is not distorted or bent first before buying a new axle. You can use a dial indicator or a stationary point on the axle housing back plate and measure any variations with a vernier once you rotate the axle in its fully inserted or extended position 360 degrees. I would guess, not positive, but anything less than a few thousands of an inch is normal in a used vehicle and it should work fine.
As for getting the axle out in the first place it takes a really good penetrating oil (PB Blaster, Knocker-loose, ETC.) and a high quality slide hammer with the 3 point fanged adapter once the 4 bolts are removed of course. Oh, and lots of elbow grease is required. Be patience with the penetrating oil and apply it several times after some short tries in between using the puller to rattle things up. The axle will come out.
You really should replace the bearings and holding collar as well at the same time as the seals because that outer race is whats most likely holding the axle in and your beating on it. They sell them in a kit at most auto stores. Don't forget to have them pressed on in the correct sequence or it sucks doing it all over again.