Wheel cylinders and brake parts in general are best to change in pairs. If one side is bad, the other side may not be far behind.
This is a "while you're at it" situation. If the shoes are soaked, replace them. Some guys wash them with brake clean, which is ok but not my choice. Look at the brake hardware too, the stuff does wear out. You're best off getting the set that does both sides, it'll be nicer to reassemble.
Leave one side of the car assembled and do one side at a time so you can take a look if you need to.
Tips: The longer brake shoe goes on the back of the backing plate. I always start with the back shoe, which is hooked into the emergency brake. Lubricate all metal to metal points with high temp white grease or brake lube. This includes the brake adjuster, backing plate contact areas, emergency brake hardware. Just a thin wipe is all you need.
Bob