Take the door down dry it completely then go ahead and sand over the existing laminate.
How to repair pressed wood cabinet doors.
Then remove the clamp and plastic backing.
Scrape each surface of your cabinets doors and drawers using a firm circular stroke.
Then fill the glue injector with the wood glue and apply it where the piece broke off as well as on the piece itself.
When the back of the door is completely flat glue on a new sheet of laminate.
Select the right type of primer or you will eventually end up with rampant flaking and use the proper application tool or you will see brushstrokes in the finish coat.
Sand the patched area with a medium grit sanding block.
Wait several minutes for the wood glue to get tacky and press the piece in place.
Applying laminate to particleboard cabinet doors a second strategy works best if the swelling mostly affects the back of the cabinet door.
To remove the current finish or paint get a sheet of sandpaper.
You can also use a sanding block if you prefer.
Remove the sanding dust with a vacuum.
Use a tack cloth or damp rag to remove dust after sanding.
Allow the glue to dry for the appropriate length of time outlined on the package.
It will continue to get worse as it absorbs moisture from the air.
Affix the broken piece if the piece is still attached to the particle board then dry fit it first to determine how well it will sit.
The cabinet doors and the surface of the frame will all need to be thoroughly cleaned with soap and water or a cleaning agent such as trisodium phosphate to remove dirt grime grease and body.
Water damage causes the fibers to swell and weakens the wood considerably.
Use a 120 to 180 grit sandpaper to sand your cabinets doors and drawers.
There is no way to fix pressed wood.
Unfortunately pressed wood is ill suited for adhesion and will reject a painted finish unless it is treated with primer beforehand.
You may want to use an aerosol glue activator to help keep the repair strong.
Push the separated pieces of the cabinet back together and use a clamp to hold the two pieces together.
If it s just the doors i would definitely remove them.
Mark the doors and cabinets with tape where they go.
Prime with a stain blocking primer like zinsser 123 kilz or bin and have it tinted to the color of the top coat.