does anyone know how hard it is to repair a fuel sending unit for a 2000 blazer?

 

the hardest part is dropping the tank. need a jack or stack of boards and remove one board at a time to get it down.
after that the connections are a pain, mark them and you should be fine
then remove the retaining ring on the pump, be careful to not destroy it.
clean around top of the opening to make sure you dont knock crap into the tank.
i found using a small hammer and straight screwdriver on the ring worked fine.
install new pump.
put it all back together. roughly 2 hour job depending on corrosion of bolts and mechanical skills.

do a search on the site, should be able to find alot more detail if you need it.