When installing a cooling system it is best to call a licensed HVAC contractor to handle the job. There are complicated factors involved in the installation process. First, ductwork should be considered if you have it. The last thing you want to do is put a hole in your ductwork and have higher energy bills.
Refrigerant in a system makes things tricky too. Adding improper amounts of refrigerant damage the system. You need someone who knows what they are doing. Also, handling refrigerant requires a license. Do you really want to study and be certified in that?
Another element of AC installation is the after care with it. After the AC is set up, it needs to be maintained over time. DIY AC installation always follows with big AC repairs quickly coming around. The last thing a homeowner wants to deal with is an immediate AC repair. Most HVAC businesses will put the system under a warranty and the repairs will be free! I say it is worth doing that!