National Characters Again

Hi

I would like to use TOAD 11.xx with my 12 years old database and
applications.
My database is 10gR2 but applications are very old. TOAD 11.xx do not
show my
local characters ( Macedonis kirilica ) correctly. I know, that I should
convert my
database to UTF to use TOAD 11.xx but there is my question.

How will this affect my 12 years old applications ??
I have no source code so I am not able to translate my applications.

Thank you and best regards.