I dont know for sure but i think the compressor has to be fairly close. On mine, the compressor is directly behind the wall where I have my unit placed.
As far as DIY, I wouldnt do it. The company that installed mine had to pour cement for the unit to sit on, drill into the house and run the ducts. Also had to have an electrician come on and wire everything up. On top of that, they had an inspector come out and make sure everything was done to code.
If you are a pro and doing stuff like that, i guess it wouldnt be to bad, but if you arent, i wouldnt attempt it.