If you ride on some pretty nasty trails theres nothing wrong with springing for a full suspension. Do you need it? no, I raced Downhill on a hard tail. I got my bell rung every race, but you can do it.
If you are going to look at a full suspension you are going to need to make your wallet a little deeper. If you want something decent to beat on, plan on spending around $1000+. You can get some cross country full suspension rigs for a little less, but you wont be happy with the limited ammount of travel.
I recomend going for a nice hard tail. Again, you are going to want to spend some good money on one if you want to ride it hard and not replace it every year.
I ride/race everything from Downhill to cross country to road bikes. On my Downhill bike its 8" rotor Hydraulic or nothing. On my dirt jump bike its 6" rotor Avid mechanicals. On one of my cross country bikes I have disc, the other I have V's. If you really feel like you need more stopping power go with hydraulic discs. You probably only need 6" rotors. If you want to buy cheap get Hayes hydraulics. You start looking at Hope, Magura and things...you are going to price your self out quick.
Ill only ever buy Avid Mechanicals. I have them dialed in better than any Hydraulic brake I have had. I know trials guys that have them so that if you touch the lever you will end up on your face. The biggest difference between Hydraulic and Mechaical is the feel. When I ride my Downhill bike I have to have Hydraulic because they are easier on the arms. When you are holding onto your bike for dear life for 20 min down a mountain, you want Hydraulic.
Mechanicals are good for bikes where you arent on your brakes the entire time. Your arms wont get tired out as fast.
Brake pad wear varries. My downhill bike I change them 5 times a season. My cross country bike Im on my second season on the same pads.
Theres lots more, but this post is already really long. PM me if you need help.
I dont have a picture of all my bikes, but heres a few pictures.
Im the guy in the white shirt. The guy with the chain saw is Ray and the guy in the green behind me is Nick. We pretty much built Rays Indoor mountain bike Park.
www.raysmtb.com
Heres my Downhill bike.