96 Grand Voyager 3.0L speed sensors

Hi there,
from BC Canada, I have a 96 grand Voyager 3.0L 227K, need to change the 2 speed sensors (SC103 input & SC104 output), my speedometer is completely dead.
I know these sensors are cheep but I can't find the place where they go, can I do it myself or need a shop.
Can I still drive the Van with that problem or is a minor issue?
Where they are located?
thx