At one time it was assumed that the rf hub had to be replaced. Someone discovered it didn't. Verify that your circuit board on the fob has all the contact points installed (I believe someone posted pic's above) if so, just buy the new overlays with remote start (off Amazon, I think they are around $10-15). Check connector c1 pin 11 at the bcm and verify it's populated. If so then you can simply splice into it and ground it. If you want the hood latch, you can buy that but you'd either have to find a junk yard to get the hood latch harness or find the correct connector and pins to make your own. A lot of places that sell the particular pins and connectors have recently put a large minimum quantity on everything. A year and a half ago I was able to buy pins for the bcm and front end module connector (under the fuse box that has lighting/hood latch) at any quantity. Now most have a 100 minimum. Which depending on the pin might equal out to $20-50 for a 100.
2018 2500 6.4L Hemi Tradesman
1990 5.9L 12v Cummins W250