I say try it. Just take appropriate precautions.
If you screw it up, you'll have to buy a pump anyway. If you discover something, then you'll be ahead.
Sealing the pump afterwards would also be my concern.
Do these pumps have a core value? If so, some way, some how, they are taken apart and rebuilt.
Speaking of that, possbily you could locate a rebult one that might keep the cost down.
Keep us posted,
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)