Personally i would pay a pro to put it in. We had a pro do ours 10 years ago and it still looks perfect. yes, the corners are concreted in the ground and my posts are 8' a part.
Mine is Red Brand.
We crossfenced one pasture about 5 yrs ago ourselves with a less exspensive brand(don't remember what it was at this point) and it is ok, but not as nice and tight as the pro did it.
The worst part is that this cheaper brand at half the age of the Red Brand, is all rusted out and we are going to have to replace it in the next year or two while the Red Brand is still silver and red!