All I did was tap the file from Root Explorer, choose "install".
I get a dialog that asks to "install"? Then Replace "OK"?
Then I get the standard Market "install" or "cancel".
Then a choice of "open" or "done".
I went into Settings... applications, found Market, and uninstalled updates. I reopened Market and installed it again to tell you what it said.
Maybe you need to redownload it.
If you don't install it now, it'll get pushed to you in a few days anyway.
Are you running stock rom?