There are ways to non-destructively test for cracks and voids in various structural elements. Planes already go through very stringent inspection and maintenance cycles so various physical factors will already have a well-established baseline to compare to.

Some speculation; the damage may be far less than you'd think. Aircraft are (generally) designed to fail gracefully and the front landing gear is a mechanism that sees a lot of force during landing. I can't tell if the assembly folds back into the landing gear bay or if it penetrates the fuselage without collapsing.

A whole sack of shit went wrong if the fuselage fell directly onto the gear assembly but if the landing gear "simply" folded back into the bay it could be a relatively easy repair. Airframe loading is extremely well-characterized and engineers are already running the numbers on what forces went where.

All that said; fuck McDonnell-Douglas. Boeing "acquired" them back in the 90s. Somehow the MDD board of directors (comprised of businessmen) took over leadership roles formerly held by people with engineering backgrounds. A lot of the failures and poor reputation Boeing has suffered in the past few decades are very likely related to that leadership change.