LS9698

I'm planning on replacing the fuel pump on my 98 LS today, (attempting).
While I wait for its delivery I think I should do some prep work.
1: disconnect battery.
2: ask if it's accessed through the trunk or behind the back seat. My search didn't reveal the answer so I'm looking for a quick reply.

3: I will likely have more questions as the job progresses.

4: The gas gauge isn't accurate and I can't find a sending unit or sensor listed online to replace.

Any help appreciated.
Thanks

aptoslexus