young Ed
Veteran
that is the one by the looks and sounds of things you have a free wheel with cassette (been learning all about this recently due to my own rear wheel) so you will have or already have something roughly looking like this once you have cassette offAlso how will I know if this.... http://www.ebay.co.uk/itm/360495130973?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
will fit on the back cog?
View attachment 34539

and then if you want to get free hub body (the black thing with splines on it) off to clean or replace, you need a allen key anywhere between 10-13mm. like below
you end up with
the kit you linked to on ebay comes with spacers you slot on free hub body either side of included sprocket to adjust chain line in accordance to front chain set
guides on youtube
Cheers Ed