Fuel tank

Hi all just starting out and new here,

i have just pulled out my mk1 1.8 gti from 17 years of storage. I'm in the process of trying to get her running I have had to get a new fuel pump so I wanted to check out the condition of the tank before putting in the new pump it's not great. Just wondering about trying to wash /flush it out in place I don't want to have to take it out if I can avoid is there a solution I could use I've heard people using vinegar to clean out fuel tanks. I thought maybe of getting a drill pump to wash / flush a solution through it. Any advice would be great. 

Cheers