Help after hack...

Hi there,
my forum was hacked last night - i believe nothing dramatic -
After i replaced it with my backup everything looks fine - but now i have some questions - hopefully you can help me.
EDIT; Server says "The requested URL /web/news_index.php was not found on this server." - thats true but i havent also one in my backup <img>
Is it possible to download IM141 new and extract only this file and use it without problems?!
this are my first steps.
changed root ftp pass
changed root sql pass
mailing to users to change password (is there a possiblity to force them by the forum itselfs? )
is this everything i can do ?
i looked at the "config.php" with all my connection infos. is there a possibility to get it encrypted?
Are there other security options? Or an option to proof if nothing was changed e.g. to snif passwords or usernames?
Sorry, but my english isn ´t good and i got no idea what can i do against this :-/
P.S Offtopic - can i switch from IM1.41 to IM3beta without problems? i only want to keep my forums topics, post, users etc. (history) - configuration isn ´t necessary.
big thanks in advance.
my forum was hacked last night - i believe nothing dramatic -
After i replaced it with my backup everything looks fine - but now i have some questions - hopefully you can help me.
EDIT; Server says "The requested URL /web/news_index.php was not found on this server." - thats true but i havent also one in my backup <img>
Is it possible to download IM141 new and extract only this file and use it without problems?!
this are my first steps.
changed root ftp pass
changed root sql pass
mailing to users to change password (is there a possiblity to force them by the forum itselfs? )
is this everything i can do ?
i looked at the "config.php" with all my connection infos. is there a possibility to get it encrypted?
Are there other security options? Or an option to proof if nothing was changed e.g. to snif passwords or usernames?
Sorry, but my english isn ´t good and i got no idea what can i do against this :-/
P.S Offtopic - can i switch from IM1.41 to IM3beta without problems? i only want to keep my forums topics, post, users etc. (history) - configuration isn ´t necessary.
big thanks in advance.