Hi Luis;
1) Yes, I would remove the DLL's path - then it can be located anywhere you like. This is an optional change BTW and just my $0.02 on external DLL handling. 
2) PB 12.5 is UNICODE and you need to watch out for all the "String" arguments in the DLL call. Even though you state ANSI (as Bruce mentioned) - the actual space and content of the REF areas are Unicode content format.
Tip: You will see that many PB commands like Blob and String for example that have a new encoding parameter (argument) that you may need to use.
HTH .. good luck!
Regards ... Chris