fuel sending unit and fuel gauge trouble

In a group this size you can get a wide range of responses. Some will get ( sort of sit ) upside down, others remove the front seat to be more comfortable while changing bulbs, limiters, etc.., from underneath the dash.
To remove the inst' panel and take it to a workbench is the proper method. The "how to" procedure is detailed in factory service manuals. Many of those are free downloads ( at Mymopar.com I think ).
Through a lot of experience I have modified their method a little to suit myself. No need to go into that though.