Front Axle Fluid Leak - 2007 LTZ

So I went in for an oil change about a month ago at the dealership and the following day I pulled out of my garage and noticed a 4" diameter puddle of dark-colored fluid on the garage floor.  Thinking that this may have been carelessness of the mechanic pouring the oil into the reservoir, I didn't think much of it.  Checked my oil level the next morning and moved on.
 
However, a couple of days later and every two or three days after that until now, I have noticed a drop of this same dark-colored fluid on my garage floor which shows up in the same spot.  I crawled under my Tahoe and noticed that the fluid is coming from the passenger side front axle.  It is not coming from the differential housing in the center, but it is coming from a small slotted area on the passenger side where the axle itself appears to be visible just before the 'shock' looking units near the wheel (there is a large bolted connection of the axle casing right here as well).  This same small slot occurs on the driver's side, but is completely dry where the passenger's side is dark, mucky, and leaking.
 
Does this mean I have a leaky front axle seal or what seems to be the issue here?  Is this something to be worried about?  Could this be something that the dealership created during the routine check-up for the oil-change?  I haven't discussed this with the dealer yet but plan to this week sometime.  Just looking for some insight and expertise before I head in.  Thanks for the help.

Due to the location of the leak (passenger side) and the fact that the leak from what you said; is now just a drop, I would first suspect that the mechanic may have just spilled some oil down the side of the engine when he was refilling the engine and it taking its time working out of the nooks and cranny’s.


It's pretty easy to determine if the leak is engine oil or differential fluid, if it is front differential fluid the fluid is 80W90 which is very thick and will have a strong odor, engine oil is much thinner and not so smelly.  

Chevy dealer put grease in the top of my shock instead of the grease fitting on a Silverado I had. Even dealers are susceptible to the quality of their help.
 
Try to get back to the dealer as soon as you can.

Hey the top of a shock sort of looks like a grease zerk.  Cut the poor guy some slack. 

ZX, I actually felt the top of the axle and there was no fluid coming from above (even with a visual check).  I just have a hard time believing that oil just happened to spill right at that slotted location and is still dripping over a month gone by now.  I did smell and feel the fluid and yes it does feel much thicker than oil and had a distinct odor as well.
 
So if this is axle fluid, do I have a big problem here?

Not a huge problem but you will want to have the axle shaft oil seal replaced.
This is covered under your GM 5yr/100,000 mile powertrain warranty.

Thanks for the insight.  I'm about due for another oil change so it's a good time to get this done as well.  Do you know if they have to pull the entire axle off to fix this?  If yes, can this bring further problems down the road?

Replacing the seal is not all that technical; the nice part is that most dealers powertrain technicians are generally pretty good.
If it were my Tahoe I would have no reservations about the repair or the likeliness of future problems as a result, it’s a simple leak have it fixed end of problem not big deal. 

Update...
Got an oil change today and had them check the leak out.  It is for sure a front axle seal leak and I have it scheduled to be replaced on Tuesday.  Should take 2-3 hours.  Dealer said they've seen it in a couple of other 2007+ Tahoes/Silverados.  Thanks for the help!