Any veterans out there want to take a stab at this one? ( For us newbie diesel owners that aren't mechanically inclined - YET - )

What would a list of jobs look like for someone looking to improve their mechanical knowledge on working on diesels? (ie. start with oil change, move to something harder, followed by something harder, etc.)

Basically looking for things to work on in increasing order of difficulty on my vehicle. I see articles all the time that say "if you aren't comfortable with xxxx, don't try yyyyy." So how do you get comfortable doing those things without taking a course?

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79 300SD - $50 out of pocket purchase
03 Dodge Ram 3500 CTD
2003 VW Jetta TDI