Starter failing. Can I diy?

Absolutely,

Replacing a starter is not that complex of a process.

Step 1. Go to your local parts store and purchase a replacement starter.

Step 2. Put on some old clothes and grab yourself a large piece of cardboard to put on the ground under the vehicle.

Step 3. Disconnect the Positive lead on the battery. You are going to be removing some wires and if you don't disconnect the battery it can throw a large amount of spark and potentially short and damage other components.

Step 4. Grab your handy dandy set of socket wrenches and climb up under the vehicle and locate the old starter.

Step 5. Locate the wires and use your sockets to remove the large and small wires from the starter solenoid. It will be the smaller portion of the starter. They may be covered by a rubber boot that you need to move out of the way.

Step 6. You will see that there are a couple of bolts holding the starter to the bell housing. Usually it is only 2 bolts. and on a GMC i am gonna say they are likely a 15mm socket. Remove these.

Step 7. As you begin to remove the bolts you will see the starter start to drop and loosen. Be careful not to drop it on yourself as you loosen the bolts and take note if any shims or small plates come with the original starter.

Step 8. Clean the area and inspect. Grab the new alternator and do exactly the opposite of the instructions to install the new one.

The starter bolts should be torqued to 37lbs of torque. You should be able to achieve this easily with a decent socket wrench.

I am going to include a video from youtube of someone else making this repair. However anyone can change a starter.

Video 2014 GMC SIerra Starter Replacement.

I hope this helps and good luck!!

Moe