Ok, first off you will need a press to change the cv boots out on your axle not a hammer. You have to press off the inner spider bearing, don't want to go hammering in the bearings.
The groove for the axle snap is on there. Grab your axle assembly from the back and pull the axle forward towards the outside of the hub to expose the groove.
If you just had the hub rebuilt or pulled apart the tolerences and spacing will have changed. Slightly different dimensions on new aftermarket parts plays a part in this. Didn't they put in a new crush sleeve? That has to be the proper size to space out your inner and outer bearibgs, if it's to big your axle will not go deep enough to expose the groove for the snap ring.
With that said make sure the spindle but is at proper torque setting. This will pull all the bearings closer together exposing more of the axle splines. If that fails to work you you can put the whole axle assembly with the whole spindle into a press to push the axle through that little bit you need to get the snap ring on.
You could always pull the axles out and drive 2wd for a while.
SAS is above your head imho.