There is a difference in labor between following MB repair manual and taking shortcut.
In MB's repair manual, I remember there are more than 30 pages for rebuilding PS pump, I believe it can take up to 6 hours.
The shortcut is to only remove the frontal half of the PS pump, and change the frontal main seal and some inside seals, it takes less, but I would still think 4 hours is the minimum for such a job.
I did my pump by myself a year ago, I took shortcut, it took me, a DIYer, 8 hours, part cost is something like $20.
99 BMW 540i 6-speed 110K Km
03 SAAB 9-5 wagon 80K Km
92 400E (Sold) 245K km
Still missing the days with the Benz, it kept me busy.