According to our system here, the "custom" amount of a burial is anything over 50'. Anything over that is a "custom" work order, and that runs about $50. That is really the only correction I have.
No prep work is needed on your part as far as trenching for the drop, or setting a pole. Having someone come out and mark utilities is a great idea if you can do it beforehand. This is more to save time on your part.
My suggestion is to always disclose your intention on the installation, again just to save time for you and hassle for the tech.
DISH will do this directly for you, btw. One thing to make note of: First, have the tech tell you what it is he is going to do as far as the installation before any drilling. Discuss any changes you would like to make before the first hole is drilled. He will tell you what can and cannot be done, not to mention go through any work order modifications that are necessary. Some w/o modifications cost additional. Each "custom" mod runs about $50, and so long as you understand that things will go smooth. The modification will be either due at the time with a direct DISH rep, or possibly the next bill. Also, at the end of the job, make sure that it is to your liking before signing saying the job is complete. This insures that you have the installation you want and you say that the job is neat and tidy. Once you sign saying the w/o is complete, any changes come at a cost to you.