Haynes manual is straight forward.
I replaced mine a few weeks ago, 1987 LR90.
The three bolts on the front bracket are quite difficult to get to.
I had to cut my rear brackets off & weld them back because my original nuts & bolts wouldn't undo after 23 years of road salt...
other than that 'tis a 1 spanner job...
If you get stuck pm me :-)
Can you post more info on the guage & sender you fitted LG?
Or post some pics too.
I too have a duff temp guage...
I've tried different senders but none work properly.
The guage tests out ok.
Thanks
M