yppur extrude problem is a common issue in maya im afraid. what you need to do is to extrude faces that are planar, on the same exact plane or close to it, so that maya can move them uniformaly in local space.

here is a tool that sort of extrudes along normal

https://www.highend3d.com/maya/downlo...ygon/3157.html

this one moves/rotates/scale along normal

https://www.highend3d.com/maya/downlo...ools/3717.html

you can do a zero length extrude then move the newly created faces perfectly up in the normal direction of the preceeding faces.

good luck.