I didn't give a second thought to taking an unmodified '04 6.0 (~200k miles on chassis, 50+k on engine) down with my family. Has yours broken down since you've done your mods? It really sounds like you've covered all of the bases. Just take a reasonable spares kit (misc sensors (ICP, crankshaft), fuel filters, etc.) and you should be fine. Also, I've found mechanics in Mexico to be top notch and very resourceful because they can't afford to replace everything.
I just returned from Baja this week in a beater truck with 250k miles. I thought about it but it did not stop me. Other than the various attempted beheadings, it was great!
Eager to hear more details about your trip. When are you going? Surfing, fishing?