hi,
this article on petri should give you a fair bit of understanding and few examples on how to use repadmin.
http://www.petri.co.il/tracking_ad_change_replications_using_repadmin.htmand this link is added on the same page which is basically a tech net article on the repadmin examples.
http://technet.microsoft.com/en-us/library/cc773062.aspxwould recommend first reading the article on petri's website and then refer to the examples on technet, and create your queries accordingly.
bhanu