New you can forget full suspension. You pretty much need to double your budget to get a decent new full suspension. You can find a pretty good hardtail new for $1k though. With hardtails the name on the frame barely matters. Full suspension it matters more sense everybody has their own rear suspension setups. Basically look for something with at least midrange drivetrain bits on it (x5 sram or deore shimano) or better and try to avoid suntour suspensions. For $1k new you can probably find a hardtail with a rockshox recon silver or at the very lest a XC32 fork. $1k can get you a nice used bike but it helps if you already know a decent amount about what you want and are looking at.
Bicycle Blue Book - Used Bikes
that site can help some
As for the prostate thing. Bike shorts, try different seats, and adjusting the angle of the seat.