I have a twist type shower diverter and it only works in the position for the shower and not the tub spout is there a fix for this problem without replacing the diverter or do I need to replace the diverter? If the diverter needs to be replaced how hard is it to do?

By "twist type shower diverter" I assume you have a three-handle tub faucet.
Replacement or repair is a fairly straightforward task. How difficult it is depends on you, what experience you have and what tools you have.

Remove the handle. You may or may not need a faucet handle puller. It all depends on how corroded the stem is under the handle and how long it has been since it was last removed.
Remove the stem sleeve or cover. Some simply slide off, some screw off.
Remove the escutcheon cover or plate. Most simply slide off.
The first nut you see around the stem will be the stem-packing nut. That keeps the water from coming out around the stem. The next "nut" you see will be the shoulders of the stem body. Using a tub faucet wrench or socket, unscrew that. The stem and body will come out.
With a flashlight, look in the valve body. You should see the seat. That's the thing the washer presses against to close off the water. You should be able to see if the seat takes a square tool or a hex shaped tool. Using the proper end of the seat wrench remove the seat.
Take the diverter stem and the seat to a good hardware store and purchase the necessary replacements parts and a new seat. You may want to simply purchase a new diverter stem. Also purchase a small container of plumbers grease.

Reinstall in reverse order. Grease the threads of the diverter stem. Install diverter in the open position, that is, screwed out, so that the washer does not press against the seat as you screw the stem into the valve.

Tub faucet wrenches or sockets usually come in a set of five.

Let me add a image to Harolds excellent discription. Tom