remove replace diesel in tank sock

[nota]

how to remove and replace the in tank filter ''sock''
in a 83 300sd

we have changed both filters under the hood
car idles and sometimes runs fine
small clear filter is not filling completely or quickly
car is has intermitent power loss [will not rev over 2000 rpm in gear]
if allowed to idle power comes back after a minite or two
I am thinking partly block line or sock in tank

tips or tricks to get at the sock and clear the lines
other things this could be caused from??