Many codes specify burial of conduit 6" below the frost line, and a pole to be 1/3 below ground and 1/3 above ground, with a bag of concrete per foot exposed above ground if you're installing in soft or sandy soil, and allow a bit less if installing in hard, clay, rocky soils.
Kind of silly to go to all this effort and have your conduit freeze and crack, fill with water and freeze again, or to have your pole lean or get pushed up out of the ground. Might take 5-6 years and you might be able to correct the dish position to accommodate it, but why not do it right?
In certain areas with sandy soil and high wind loads, 160lbs of concrete would be sadly inadequate.
Good thing I didnt bring up brazing some rebar to the bottom of the pole and a 12" metal plate at the surface level...
As far as cost and time, I cant say for sure as I've only done this for myself. As someone who has a vested financial interest in a construction company, I'd advise everyone doing something like this to identify their local codes and best practices and follow those. You'll probably do better than advice from someone on the internet who has different soil, different wind, a different dish, used a different pole, different concrete and/or any of the other plausible variables.
Heck, if its the physical labor thats the issue, you can rent a small auger to dig the hole and a small ditch witch to do the trenching at your local lowes or home depot. Many of the larger ones rent tools like this for ~$35/hr. Just make sure you know where your gas, electric, cable and water lines are before you dig.
Heres a good source for details:
http://www.dslreports.com/faq/2689