It's awesome to be able to work on your own vehicles.
I've done it with help from my father for my entire driving career.
Currently have a Ford Focus with a transmission control module that's not working.
Took it to Ford, and they ordered the part it's on back-order up to 6 months.
I found it online for a couple hundred bucks, and looks like I'm gonna be installing it myself. The only caveat is that it needs to be programmed and synced with the central and engine computers, but luckily I have a guy for that too.
Biggest takeaway though, the newer the cars the more difficult it's going to be to replace digital components. And it seems each year they're making more of these cars digitally controlled.
RE: 2004 Jeep Grand Cherokee: Head gasket and timing guides.