"If I use base42_encode() to encrypt this information, does anybody know how the this information (name/value combination) can be retrieved by the new script? "
baseXX is not encryption, it is encoding, and anybody can 'decode' it.
the 'smartest' way to 'hide' url data for prev/next buttons is by storing the query in session data, and only send the pagenumbers through the URL.
Q: why are you worried about end-users knowing your field/code structure? The URL only passes parameters, which say absolutely nothing about the itnernal structure of your script/database.