You can remove the cover on your key to see if the remote start is present, you'll notice when you remove the cover that the circuit board will have a silver circle where the buttons are on the key pad. If you look at the underside of the rubber keypad you'll notice the little button "strikers" (or whatever they are called) that make the button work, you'll only have "strikers" for the buttons that are present on your fob. So if you have the circles on the circuit board where the remote start should be then all you need is to super glue a "striker" in the position to use your existing fob.
To add remote start you can just use alfa. You'll need to enable remote start, make hood ajar present, change hood ajar to 500ohm (you can try with or without changing this), you'll have to ground the hood ajar bcm wire (tells the bcm that the hood is closed all the time), cycle key/close open door to allow the system to take the changes. double click where the remote start is on the fob and your truck should honk 3 times and start. total cost not* including alfa is $10ish just to get the button striker, some wire, and an eye for the wire.
Alternatively you can buy the hood switch instead of grounding the wire if you don't feel comfortable cutting it, adds to the cost but makes it more oem. You can even just buy the kit that includes 2 fobs with the switch and still use alfa to activate it.
This is the reason I downloaded alfa, couldn't believe I could have factory remote start for such little money
