As long as the latex paint is fully adhered and the wall is in good shape you can go ahead and repaint with your new color and sheen. Here is what I do to <a href="https://www.house-painting-info.com/interior-paint-preparation.html">get ready to paint an interior wall</a>.
Preparing the wall for repainting depends on its condition and cleanliness.
I always recommend priming before applying latex over oil base paint; this assures full adhesion of the new paint. So the first thing you need to do is check and make sure the latex paint is fully adhered to the wall.
This is an easy test. Use your fingernail and scratch at the paint is several places. Another way to check is to apply a piece of regular masking tape to the wall and quickly tare it off the wall. If any paint comes off you have a serous problem that isn't easy to fix.
Assuming the paint is in good shape, the next task is cleanliness. Sticky areas, greasy fingerprints and stuck food particles will interfere with the new paint. If any of these conditions is present use a soft cloth with mild soap and water, rinse well and allow to dry.
I <a href="https://www.house-painting-info.com/switchplates-outletcovers.html">remove all switch pates and outlet covers</a> plus any other items that are easily removed. This can include lights and shelves. It's easier to paint without obstructions in the way.
Now is a good time to <a href="https://www.house-painting-info.com/masking.html">cover thing up and mask some items</a>. Prevention is better than cleaning any day. All that is left is <a href="https://www.house-painting-info.com/drywall-repair.html">fixing imperfections or repairing any damage</a>. Always prime any large repairs.
That is it! In the future prime all surfaces before applying latex over oil base paint.