Impala Oil Leak

Make: Chevrolet
model: Impala
Engine: 3.8 V6
year: 2000
mileage: 169000

I know a lot mileage but the car has been a great car since I drove it off the lot. Anyway, I am a wanna be mechanic and I have replaced the radiator and other parts on my car b/c I just dont like paying so much for labor when I know I can do the job. I took the car to Goodyear/Gemini service center to see where an oil leak was b/c I have noticed oil deposits here lately on my driveway, the guy there told me after doing a dye test that it was the head gasket it needed to be replaced and or the oil gasket. But he would start at the top and replace that. So my questions are: 1. Is this a normal spot for an oil leak? He quoted about 700 bucks to do the job using AC Delco parts no problem with parts but labor was like 550 bucks. 2. Not knowing how difficult of a job this is, is this reasonable. 3. If I get all the parts and want to do it my self about how long does it normally take, using a manual for Luminas which covers the 3800 series motors they used in this vehicle as well? Thanks in advance for the insight. Look forward to any assistance that can be given.