1. vinyl fencing is just fine. Fairly low maintenance, and will last a long time barring catastrophe...
2. It will be expensive either way ... Most prefab fencing still requires the anchor posts to be dug in and cemented. Your biggest cost doing it yourself will therefore be time. (yay for post hole diggers you can rent
) As far as difficulty, it's not bad at all, just alot of measuring and making sure your anchors are plumb and solid. Of course with any digging, call your utility company so they can mark out where your power, cable, gas and electric may be buried. (you might want to do this early to determine exactly where the fence will be)