Assuming that they are just doing the lower part of the sump to clean off the oil strainer I would say around an hour to get the guards off, drain the engine, get it off, refit and fill up again.
We have a dead 1KD-FTV engine in the workshop that had a blocked sump strainer among other problems.
I strongly recommend that anyone with a 120 series with that engine to get the sump pan checked - Toyota seem to be slow on picking up on this one although we hope to change that.