While you have it off, get some of those quick release connectors and install them on the fuel lines. Makes taking off the tank a breeze.
http://www.ascycles.com/detail.aspx?ID=1552
Ha, those quick connectors have a well known failure rate, enough said, read carry spares. Wish Cranky Frankie were here to comment on them.
Metric nut driver makes it EASY to remove the fuel line clamps, unless there the "one shot use" OEM BMW Oetiker brand. Simply cut those off.

If your K has the Oetiker's, R&R with a FI rated clamp ! Important, as pressure spikes will loosen a regular worm type,you have been warned. FI models have a secured nut,second pic.

Loosen the clamp enough so it slides below the nipple, slight twist with a pair of pliers on the line, if it's stubborn upon removal. Only a small amount of gas will dribble out even if the tank is full, NO big deal.
FWIW, I gave up on those silly tank retention C clips years ago. Granted, the tank may separate in a severe crash, but at the point there are"other" issues to worry about.