Only reason I ask is that I had mine done for the first time in 7 years on my boat. It was due.   The labor costs were ASTRONOMICAL!!! Anywho, I know that to replace an impellar on an outboard motor, you have to drop the lower Unit. Now, I have some mechanical skills, but I don't know if I am confident enough to tackle dropping the lower Unit. Anyone here do this themselves? If so, how mechanically inclined does someone have to be to tackle this type of routine maintenance?

Depends on the motor as to what's involved.   I've never seen one that required any great mechanical skills but would suggest you get some type of manual as a reference since this would be your first.  

The two biggest problems facing you since you say it's been seven years, sometime the drive shaft will rust into the crank, making getting it out extremely difficult to almost impossible if this happens  The other is the shift rod.  Those can be difficult to get to trying to disconnect it.  Some also hide a bolt under the trim tab, so back to the original suggestion, get you a manual, makes life much simplier.  

If it's a big motor, you might want to trim the motor up after getting the shift rod disconnected and ready to drop the LU.   Those things are heavy and having the motor up where you can handle it helps.  Helps even buches more when trying to put that heavy sucker back in if your shift rod will let you have it trimed up.    

After seven years, get a full kit, not just the impeller, most likely none of your gaskets and seals are going to be reusable and lube it with some Lubriplate 105 for during assembly.  Grease the drive shaft spline

On some Merc's, make sure you have the shifter in the recommend position before dropping the LU.

Only reason I ask is that I had mine done for the first time in 7 years on my boat. It was due. The labor costs were ASTRONOMICAL!!! Anywho, I know that to replace an impellar on an outboard motor, you have to drop the lower Unit. Now, I have some mechanical skills, but I don't know if I am confident enough to tackle dropping the lower Unit. Anyone here do this themselves? If so, how mechanically inclined does someone have to be to tackle this type of routine maintenance?

check your pm  s

I had this maintenance done to my boat already. I had it done in early Spring. I was just wondering if it is feasable for a guy to do it himself.

RL, you can definitely do it yourself. i got 3 quotes to service my outboard, and the cheapest price i got was $350, and the most expensive quote i got was $500. do yourself a favor and by your engines manual. i bought my engines manual from ebay for about 20 bucks. after the 3 quotes i got, i went to the marine center, bought the waterpump kit which included the impellar, gaskets, and everything i needed plus i bought the oil and the total was 45 dollars. i did the job myself and saved a boat load of money for the bait monkey. do what i did and call some mechanics and pick their brain, most of the guys will give you helpful tips.