How long would the Earth last if the sun became a black hole?

[Lord Torath]

If the process means putting a stellar mass black hole in the sun's place then we'd go into a highly eccentric orbit and potentially the Earth would be torn apart by tidal forces as it approaches periapsis (perihelios? periblackholeius?).

When you say "stellar mass" black hole, do you mean a black hole with the mass of the sun? Or one with several to several-dozen times the mass of the sun? My first impression when you say 'stellar mass' is the mass of the sun, but in that case we wouldn't notice anything other than the sun has stopped shining. If you mean "several to several-dozen" solar masses, then yeah, our orbit will rapidly decay and we'll get ripped apart when we hit the black hole's roche limit.