The truck carries the parts that fail most often on openers from this era: drive gears and sprocket kits, standard logic boards for the major current brands, wall control units, and safety sensor pairs. What we don't carry, and usually can't get same-day, are proprietary boards for opener models that stopped production years ago - if your unit is one of the originals from the 1970s or 80s that somehow never got replaced, that part may need to be special-ordered, and honestly, at that age, full replacement is often the cheaper and more sensible route than chasing a discontinued board.
That's the one limitation worth saying plainly: we'd rather tell you to replace an ancient opener than charge you to nurse a board back to life for six more months.