out-dated php-files?

Hi folks…
I recently got my wordpress site at biophoto.no hacked and blocked by domeneshop in Norway :(. After calling them and examining the log files that they sent me, they said I needed to update the following files (copy from the log) as they were outdated:

Domeneshop/Domainnameshop autogenerated at 2011-11-01 11:27:12
# Old software found: 2
PHPMailer 5.1 – out-dated: ./www/wordpress/wp-includes/class-phpmailer.php
PHPMailer 5.1 – out-dated: ./www/wordpress/wp-includes/class-smtp.php

How can I do this? I am not into these things and really need help here.

Also the following files were hacked and need to be fixed (from the domeneshhop log):
# Domeneshop/Domainnameshop autogenerated at 2011-11-01 11:27:12
# Damaged files found: 5
Backdoor (1): ./tmp_4090369912738966.php
Backdoor (1222,1157): ./www/guestbook/gbook.php
Backdoor (1): ./www/tmp_4090369912738966.php
Backdoor (1): ./www/wordpress/tmp_4090369912738966.php
Backdoor (1): ./www/wordpress/wp-config.php

Can I replace the files with the original copies on my PC? Will that solve the problem?

I appreaciate all help very much…!
best
Alf J