I did mine today... With the seat still in the truck...
If you have yet to take one out:
1- move the seat all the way back and lean the seat fwd.
2- use a small knife or flat head screw driver to seperate the locking piece holding the leather together... (black) inside the seem. Between the seat bottom and the back...
3-once the back of the seat is open... Reach up and into the seat... There is a c-type clip at the base of the pin holding on the armrest. There is a small rubber o-ring holding the clip from coming off, but not all that important!
4-once u find this clip with your fingers, you will notice it seems to be like a cotter pin but it's not. With your finger on it use a long flathead screwdriver and push on the pin type end and the clip will slide off.
5-the armrest simply slides out.
6- push the new armrest into place all the way. I put mine into it's up position.
7-I had to use both Hands to put the clip back into place. As you now know there is a metal bar on that side of the seat. Push one hand infront and with the clip on your othe hand feel for the notch whe you believe the clip to go. I hope u have patience. I put the clip on in the opposite way it came off but I don't plan to remove it ever again anyway. Once you have the clip into place slide the screwdriver in and push the clip back into place. And the rest im sure u can figure out.
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the clip can only go on 2 ways. The way it came off and in the opposite direction. The pin is notched so if u find the grove you find it's place.
Took me about an hour start to finish.
Hope this helps if you need additional info call or txt
904-361-8800 pacific time