What does error F1 mean and is it expensive to fix

Hello there
The f-1 error is comng from the fflood switch meaning it is not recognizng the level of the water in the machine
First thing you need to do is pull the front panel off the drawer, :
Fisher Paykel DD602 dishdrawer with the front panel removed.
With that front panel off, pull the wire harness connectors off the main control board (lower right-hand side) to inspect for junk and debris
If nothing is found
The next step to remove the botton drawer from the unit so so you can inspect the switch itself
In order to do this, You had to remove the wire harness cover on the underside of the drawer.

Fisher Paykel DD602 dishdrawer, looking at the underside of one of the drawers with the wire cover plate removed.
With the bottom cover off, unclip the wire harness, fill hose, and drain hose. Then unclip the linkage at the back of the drawer and lifted the drawer off the slider arms. All this to expose the flood switch, shown on the left-hand side of the bottom panel in the picture below:.

Fisher Paykel DD602 dishdrawer with the lower drawer removed. The flood switch in mounted on the base, left hand side.
TAKE NOTE OF the positions of the wires on the flood switch and removing them, unclip the switch housing from the base panel. The switch housing contains one switch for each drawer. The switches are wired normally closed (NC) and each switch has three spade connections, so it's important to note where the wires went. With the switch housing out, ohm out both switches and ENSURE THEY CHECK OUT GOOD OR HAVE SOMEBODY DO THIS FOR YOU inspect the contacts and SEE IF they look oxidized or detereorated , evidenced by discoloration.
If it does look discolored clean the contacts as needed now plug in everything as it was originally and put in the drawers than run it to see if it does reappear if not you saved yourself about $300 dollars on having a tech come and do this ok