Please help site hacked, files re-hack as soon as uploaded!?

Hi all, my site was hacked this evening and I’m trying to re-upload all software. However, as soon as I upload the wp-admin and wp-includes folders, the modified date for all the php files in those folders reverts back to the time they were hacked and not the time I uploaded the files.

Opening of the files in dreamweaver they look fine, but is there something worse going on here I need to know about? I’m not that good with this stuff, hacks in the past have just required re-installing all files and plugins but worried that it’s still going to be hacked this time round due to the modified dates of these files.

Any help appreciated!