There are two tools (among the other which are commonly used) you would need to install an air conditioner: a pipe bender and a vacuum pump.
Pipe bender may be required even for a wall-to-wall installation (it depends on your outlet/inlet positions).
Vacuum pump is needed to remove traces of water vapors from the system and test for leaks. You should keep the vacuum for at least 15 minutes. If water remains in the system and mixes with refrigerant, your hardware will be ruined in a season. This is especially important for the inverter systems.
If you have or can rent these tools and are able to use them, then installing a split system is no harder than any other hydraulic/gas system.