I've recently started to have problems with my truck. When I went to get an oil change, the guys at Midas gave it the once over and they said the only problem I had was a leaky water valve (which would be 500 to fix, and I can't afford that right now), I figured as long as I regularly checked the water I'd be okay. After a light on my truck turned on, I got it checked again and they said it was a messed up oxygen sensor.

I don't know if any of that is related to the problem I'm currently having. Whenever I accelerate, no matter what speed, my truck shakes and it seems like it struggles to pick up speed. Recently, it's kinda died on me. Twice now that I've stopped at a red light, when I get ready to go again the gas pedal loses all function? It feels really loose, the car will still be on but it won't go, even though I'm not stepping on the break pedal either. I have to turn it off and back on again in order to get it going again. Does anybody know what might be causing the problem? And can anybody recommend any good mechanics in the Phoenix, AZ area?
I'm not really that car savvy so I don't know what motor the truck has, but I hope this is right:

2001Ram 1500
V8 Magnum
100,013 Miles

and it is a salvaged truck but I've had it for about 3 years now and this is really the first time I've ever really had any problems with it. Hope that helps, and thank you!