Yes, it goes dark! The systems that are powered on the failed side will go blank because the cross tie relay opens up to isolate the DC systems.
You can easily bring the system back online by quickly re-tuning both navaids by using the standby switch and then re-tuning them back to the ILS.
If you do it quickly there shouldn't be much deviation from the glide path. Hit VORLOC and us VS.
Jobs a good 'em.