For just 1 mount, 4-6 hrs maybe ... but I tend to work verrry slow.
This is assuming you're just using jackstands to lift the front end of the car.
I'm sure others will say they've done it in as little as an hour.
I'd suggest lifting the car frame about 15-18", so the front wheels hang down all the way. Then remove the front wheel and you'll have MUCH better access thru the wheel well.
I'd also suggest having a 2x10 wood board (or similar) cut 10" long, use this to support the bottom of the engine oil pan. You will need to jack the engine up a few inches.
I also drilled a 1" hole in the board , where the oil drain plug goes, so the wood board would sit completely flat against the entire oil pan.
Others have warned that the weight of the engine may compress the pan gasket, and so to be sure to re-torque the pan bolts (although my gasket didn't appear to compress any, and my pan bolts wouldn't take any more torque).