What the OP is asking for (IMHO) is a safe way to check for a hacked site without accessing the site, because OP is worried about putting the OP’s system in a possible compromise.
My thought: download all of the files from the site to a local folder. Look at the local files for anything unusual (assuming you have knowledge of what you are looking at).
Or, you could upload a fresh/new version of WP to the site. Disable all plugins (quickly via FTP by just renaming the plugins folder to something else). Disable all non-standard themes by renaming those non-standard themes in the themes folder.
Take a look at the htaccess file for anything unusual; replace it with a default htaccess file.
You could do further testing on a local WAMP install with the code. But I think that the above will protect you sufficiently.
After you are comfortable with the site enough to login as admin, reinstall the latest WP version. Enable only those plugins that you are comfortable with. Enable any themes that you are comfortable with.
Change the database credentials also, and remove the user called ‘admin’ (after creating another admin-level user. Remove or disable any other user accounts until you can verify them as being valid.
Good luck.