anyone give me an idea what it will or should cost to have an engine mount replaced on an Ef 4.0L sedan by mechanic?

not sure. Swapping the mount itself is easy and should take much time but the EF engine mounts are not cheap. You might be able to ge a cheaper price if you can find a cheap mount and take it to a mechanic to swap over.

does the motor have to come out or can u do it yourself ? How ?

no and yes, depend on what tools you have.

You need to lift the engine a little to do it which can be done either with an engine crane or by using a jack to push it up by the sump (use a block of wood or metal plate between the jack and the sump so you dont damage it). Once the engine weight is off the mount you can change it easy enough.

The cheapest place to get mounts from is u-pullit. If your lucky and find an EF there 2nd hand mounts are $5.50. I'd hate to think what new ones are worth...