You need to clean all the WD40 out as it's not a very good or long-lasting lube. Use a thin blade of some sort and carefully pry off the seals. Best to clean off the WD40 with an air blower but just wiping off the balls with a rag is good enough or soak in some type of solvent, whatever works for you. Add grease which will last longer than any liquid lubes. Install seals, add a thin layer of grease to the outer part of the bearing to protect against moisture and you're done. As long as the bearing is smooth and doesn't have any pits or damage it's fine to re-use it.