Can I lay laminate flooring over top of existing linoleum?
The answer to this is "look at the instructions for the laminate", and see what they say. If you have old-school hard laminate (like you find in schools/government buildings/grocery stores), then it's a nice hard surface and it is fine. If it is resilient flooring (kitchen vinyl), then the answer is read the instructions.

If you have big ridges, I'd probably just grind them down with an angle grinder.