First off this photo was taken by my cell phone and doesn't show the size well - that being said:

I am buying a house that I grew up next to. I knew the guy who built the home and dug out the pond that is in the backyard. As a kid I used to fish and swim in the pond and I loved the water lilies. Well, over the last 17 years, no one took care of it as the man died when I was a child. I want to get it back up and nice again once I buy the home. This has been my dream since I was a young but I know nothing of water plants or keeping up a pond.

-The Bad-
The wife of the guy who built it tried to fill it in once with dead trees and turned half of the pond into a swampy wetland. It also seems to have no flow to the water - completely stagnant. All the nice water plants seemed to have died - I think the fish are gone as well. Most I've seen is a snake. The water is completely muddy brown all the time. It has become a mosquito breeding ground. And I have a lot of land clearing to do to get to the pond.

-The Good-
The pond still a good size pond even after her attempts to fill it in. At least 45ft by 30ft or so I think but used to be twice this or more. (Can't see most of the area to survey it myself as it is way overgrown as seen in photo - it goes back farther) Wildlife still drink from it so it can't be all that bad.

-What I would like to do-
I want to keep it up with mostly plants native or common to East Texas and make sure I put in ones to help purify the water some - both in the sense of removing toxins and clearing up the visibility. I do want some decorate plants added in to give it a garden type feel - but I still want it balanced for the more natural ecosystem that I recall from childhood. I also want to restock it with fish but got no idea what to place in it - not pretty goldfish of course. I was also wondering what I need to do to make the water flow better. I wasn't sure if a water fall feature, fountain or anything like that would be a good idea or even works for a large pond.

I really need help as I got no idea what I am doing and I have no experience in this type of project. I expect it to take some hard work and time, but I would like it to be nice again - something to be proud of.