You can just replace the shock however, you would need to remove the actuator to re-fill it anyway. I just replaced my rear shock myself about two weeks ago and I replaced the actuator at same time. I can give you some verbal help if you need it.
I sent you a p-email with my cell phone number in case you need help.
I see you live in Alabama.. I live in Huntsville..
Yes, you can definitely replace the shock without the actuator. However, the pre-load actuator is hydraulic and there isn't a bleed valve at the top of the shock where the banjo connector is so it makes it a bit harder to bleed the air from the line. Nothing too hard but you need to be familiar with bleeding brakes and hydraulic systems to get it to work right and get the air out of the line.
As an alternative, many will replace the spring at the same time they put on a new shock and will just re-use the old actuator cap of the old one since it's the same and never need to break open the hydraulic line. Even so, you'll want to top off the fluid in the actuator as the rubber line going to the shock expands over time and many times the pre-load doesn't actually begin to work until 8 or 10. Topping off the fluid will get it working again at 1 so you have the full range of adjustment again.