I guess it's time to find out what a transfer chain is worth. I think the manual says you have to change the gasket too, when you split the case open to change the chain.
change it before you break it. When they break they will jam up in the case and take out your selectors and possibly worse case lock up your output while driving in 2wd... wouldnt be pretty if you were driving on the hwy. But will obviously only break with continuos 4wd useage.
the transfer case has no gasket. just machined flanges. you do have to apply sealant to the flanges, you can buy it from autobarn, it comes in a tube just like silicone. you also have to make sure to clean all of the old sealant off. here is a link to my post with large pictures http://www.navara.asia/d22-drive-train/3987-d21-transfer-case-swap.html
unfortunatly the transfercase pictured has the same chain width as my old broken case,
wow. try nizz bits they quoted me 900 for a newy. your better off buying the whole t-case from a wrecker. much cheeper for you to get someone to swap it rather than splitting the case and changing the chain. the gears and bearings are all press fit, and you will probably find that if you have been driving on it for a while your gears will be chewed up aswell.
good luck and i hope it dosnt end up costing you much