Upgrade 3.0.3 To 4.2.3

I am trying to upgrade 3.0.3 to 4.2.3 and i get some errors like that:

[color=#555555]PHP Notice: Undefined index: is_edp in /home/smartaki/public_html/newsite/app/addons/store_import/Tygh/StoreImport/Ult/F306T401.php on line 282[/color]

Also i have problem with encoding! The most of Greek word are like chinese!

Did you ever get a solution to this? I have the same problem :(