The rattle is more than likely clutch related, thrust bearing, fork etc, but mines been like that for 28 months now, so not to worried
The clunking on the pick up and decelaration, may not be the transfer box, could be the diff(s), or prop shaft etc, down the drive line
Same as the oil, transfer box, gearbox, and diffs dip check on the level hole, unless you know they are overdue, if they were changed recently and not has been used heavily they should be on, just check the condition of the oils