How far should my arrow and off the rest and how much money does it cost to have your arrows sharpened and inserts put in?

Depends on your rest/bow setup.

I have my arrows at 29'' for the spine, so the end of the arrow without a broadhead or field point is at the front of my riser.

If you have the inserts already, it shouldn't be very expensive at all to have your arrows cut to length and inserts glued in. if you don't have the inserts i'm sure there will be a charge for them, at the shop i shoot for inserts are 33cents/each.

It doesn't matter, as long as it's not so short that it's a safety issue. Arrow length should be determined by the spine needed for your setup. For instance, a 31" arrow will not fly anything like a 28" arrow out of the same bow. You most definitely want your arrow within 1/2" of ideal spine for your setup.

I usually go 2 inches shorter than my draw length. My draw is 30 inches, my arrows are 28 inches.

You want at least 1/2" clearance past the rest, and a full inch is really better. They can be cut longer than that to fine tune your spine, but no shorter.

Right now my arrows hang over about 4" im taking them to a pro shop will they know what lengh to cut them?

They won't know what length to cut them unless you take your bow with you and draw an arrow for them to mark.

Or you can have someone mark the arrow for you, right where it clears the rest. Measure that length from the base of the notch in the nock and add an inch to it. Then you can tell them what length to cut your arrows.