UPDATE:

Just came back from the shop, turns out it IS the driver side axle.

The oil that I notice is actually from the power steering, the cold weather here froze and cracked something...

We ordered a GS-R axle, but for some reason, it doesn't fit? I was told that 6th Gen Si B16 axles don't fit so I went ahead with the B18C, but the end where it meets the transmission (intermediate) the end on the GS-R is 'female' whereas on the B16, it's a male? I researched all over and I could have swore the GS-R is a direct fit, perhaps they sent us the wrong shaft. So for the time being, we packed in grease and re-assembled the old shaft and it works fine, for now.

Thanks for the help everyone!