Replacing pistons is very easy once you removed the engine head.

Remove the oil pan under your car and you can see the pistons by facing up.

Remove all bolts/nuts which connected to the pistons and use a rubber hammer to tap pistons one by one all the way up still it gets out of the cylinder. You don't need to take the whole engine out. Removal of pistons should be a 1.5 - 2 hour job without any special tools.