At the front lower corner of the chain cases is a large pipe plug. It takes a 3/4 drive ratchet or breaker to remove it. There is also one under the chain case just behind the rear wheel. Remove the plus from both sides. I usually just jack the rear of the loader higher than the front and just remove the front plugs.
There is a standpipe screen behind the kick panel in the cab. Remove the seat and unsnap the latches and remove the panel. You may also want to remove the narrow side plate to get better access to the standpipe. It takes a 1/2 drive ratchet or breaker to remove the top cap of the standpip. Remove the screen and clean.