Hi Veek,
The bearings are sealed on both sides, the CV joint boot seals the axle to the output (splined) side of the joint. In theory of course nothing should be leaking. What you're probably seeing is grease from the cv joint not wheel bearing.
If there's no play in the rear wheel your bearing is probably ok. If it's got any play or roughness in it's rotation then it's suspect too.
Most likely the CV boot is not adequately sealing, you might get away with replacing the clamps with the car together. Otherwise the axles have to come off and to service the wheel bearings the rear uprights have to come off.
Note: Whether you're servicing the car or building up your rolling chassis, it's extremely important not to roll the car around on it's wheels without the rear axles in place to prevent the two bearing races of the rear bearing assembly from walking away from each other. This will give you slop that won't press back together. The hub will have to be completely pressed out of the bearing and reinstalled to close the tolerances up. Trust me on this one.
If the axles are out of the car and you have to put it back on it's wheels then at least use at least a .500/20 nut & bolt and some big washers to clamp the hub to the inner bearing race to keep them together.
If you get stuck anywhere give me a call on the toll free tech line.
Cheers