Once you have the site prepared, installing a dishwasher is easy. Make the opening the correct size and test-fit the dishwasher. The cabinets on either side should be spaced according to manufacturer's instructions -- usually 24-1/4 inches.
Run an electrical cable -- armored or nonmetallic, as required by code -- to the space. Make sure it will not bump into the dishwasher's frame. A 14/2 cable is adequate for a 15-amp circuit. Make sure the dishwasher will not overload the circuit. Hire an electrician if you are unsure.
Most dishwashers come with a drain hose. The drain hose runs to an air gap mounted to a knockout hole in the sink. From there, another length of hose runs to the garbage disposer. If there is no garbage disposer, the hose runs to a dishwasher tailpiece on the trap.
The water supply line is typically flexible copper, connected to its own shutoff valve.
About an hour once the electrical and plumbing lines are run and the cabinets installed
Tubing cutter, drill, screwdriver, adjustable wrench, wire strippers, groove-joint pliers
Making simple plumbing and electrical connections
Install the electrical and plumbing lines; install the cabinets and countertop; cut a 1-1/2-inch hole in cabinet for drain hose and supply line.
Dishwasher with drain hose, flexible copper supply line, hose clamps, air gap, electrical cable, wire nuts