Hi There
..if it's anything like mine the procedure is as follows
take out the allen bolts from the top section (of which only 3 hold the part in place) and remove the lock section
screw out the small allen head grub screws that hold the main plate to the the tank (dont need to take them out completely, just 4 or so turns)
gently and with patience work the main section up and out
remove the breather hose from underside once clear of the tank
if you dont screw the grub screws completely out then there is basically nothing else to drop into the tank, and even if you do - drain the fuel first through the drain plug on the underside in the corner and you will be able to easily retrieve anything that falls inside..although nothing will
..actually, the fun part with this operation comes when putting it all together again - the seals tend to want to unseat themselves - I've found that it's best to start feeding the seal on at one side, spread two fingers and hold as much as you can while using the other hand to feed the rest of the seal round the remaining section... do this away from the bike, then carefully reattach the breather to the underside (in the one with the hole not the blank ! ), run a small amount of oil round the actual o-ring seal and then very gently and evenly place the unit back on the tank, and work with as little pressure as possible all the way around until it seats back in place.
Once there, apply some pressure while tightening the grub screws and all should be well and sealed... if you try to put the new seal on with the unit close to the tank you will find that it constantly wants to tuck underneath the unit which can be a real pain once you have been at it for 20 mins
..hope that helps
Cheers
Dano