Well, this is interesting. Firstly, welcome to the 405th!
I wouldn't expect it to cost that much. I hear price points are closer to $100-150, and a good deal of that is often tools, so the more stuff you have on hand, the better off you are. Materials aren't particularly pricy. I'm making an ODST build, and I bought a big ream of 110lb cardstock for ~$10. If that entire thing had gone towards this project, I'd need two or three of those, at most. A tub of bondo is about the same price, and I expect roughly the same coverage, maybe a little less. Truth be told, I don't know the cost of resin or fiberglass because I have some laying around, but a little google searching will get you the prices for your area.
As for building, people can knock these things out surprisingly quickly, but that depends on how busy you are and how much attention to detail you put in. If you've got a reasonable amount of free time, I'd expect you could finish a full suit in three or four months, at best. Holding yourself to a deadline, though, generally isn't a very good idea.
Visors are... still something I haven't quite got figured out, and you're right in thinking a big one like on the Security helmet wouldn't be particularly easy. I saw an EVA build once that took advantage of the indentation pattern to, instead of a full visor, have a few windows in an orange-painted dome. To make a security visor, you could try something a bit ambitious like vac-forming (which isn't particularly difficult, I hear, but I haven't looked into it myself) or you could just try to heat shape a piece of plastic into the correct shape. Someone else will have to offer you more advice on that.
Anyway, my only advice to you, and indeed to any newcomer, is to do your research. There are a lot of great resources on the 405th, and more still out on YouTube. Safety, Materials, Planning, Scaling, Construction, Painting, Rigging, Electronics, there's some form of help out there for every thing you need to do. Read up as much as you can. It could take some time, but it's worth it. Then look around at some of the builds that are currently going on, and at some of the ones that pertain specifically to your interests. If the thread isn't too old, ask questions - almost everyone is willing to lend a hand. Learn what works and what doesn't work. Every minute you spend absorbing knowledge here will make your work easier and of higher quality.
Again, welcome to the 405th, and good luck.
