changing the seal now while the axle is out is the best idea, The seal will be worn and may not mate up to your new axle properly.
The method in this video shows the basic idea, I just do not like to use the screw to push the seal out potentially scaring whatever is behind the seal.
Grinding the tip of the seal flat is a good idea so you can get deep enough to get a good bite on the seal.
I have removed countless seals with this method with not one single issue.
Yet if your not comfortable doing this job leave it alone, just make sure to coat the sealing surface of the new cv joint with a thin coating of grease.
it is always harder to get the new seal in then to take the old one out. you would want the proper tool to hammer the seal in with never strike the new seal with a hammer trying to pound it back in because you could damage the new seal.
If you have never changed a axle before you will need a good pry bar possibly two, to quickly pop the inner cv joint off the output shaft.
the cv joint is held on with a spring loaded clip either on the axle or on the output shaft sometimes they just pop right out other times they can be a complete nightmare.
Make sure the car is jacked up high enough on jack stands to get good leverage while tugging on the axle.
I have been lucky countless times and got away with using the axle and CV joint like a slide hammer while quickly prying with one pry bar and easily popped the axle out. yet each time this worked it was with intact inner cv joint.
A worn inner cv joint may just pull out of the housing especially if the boot is soft and worn. the only thing keeping the entire inner joint from pulling out of the housing and taking the boot with it is the condition of the boot and how well the clamp is holding the inner boot on the housing.
Since we know it spit out the grease, the grease will lubricate the boot and may easily slip away from the housing, so its best to use two pry bars one on each side of the inner cv joint where you get good leverage and give the bars a quick yet strong snap to pop the joint past the spring clip locking grove.
before trying to remove the splined hub away from the outer joint soak the splines down with PB blaster or WD-40.
https://youtu.be/ri8xnBnF4yk
If you need any other help just let us know.