Where are the batteries in these? In the boot?
I found with mine (boot) that the more you unscrew the easier. Also, I replaced mine with a MUCH larger unit and had to remove the battery stand that's there as well and have a custom one fabricated, but that's irrelevant.
Taking out the back seat makes it easier, but it's not necessary... and if anything, taking out the backseats is way harder then taking out the battery if you've never taken the seats out before...
Never done a 34 though, talking about my experiences with 33s and 32s...