Question 1: So is your server back running 7.5.2?
Question 2: Did you buy the Plesk license *with* Application Vault or not?
If you are licensed for the App Vault, then I would use that to install those extras (you mentioned phpmoney, webshopper, webcalendar etc)
If you do not have the App Vault license, then from a shell prompt, you would change directory to where those extra software rpm's are located (depends on your exact system).
You can locate them by doing the following command:
locate /opt/vault/
This should produce output similar to the following and will show you the proper path to the rpm files:
/root/psa/PSA_7.5.2/rpm_RedHat_9/opt/vault/pLog-0.3.2-7501.noarch.rpm
/root/psa/PSA_7.5.2/rpm_RedHat_9/opt/vault/phpAds-2.0-7501.noarch.rpm
/root/psa/PSA_7.5.2/rpm_RedHat_9/opt/vault/phpBB-2.0.11-7501.noarch.rpm
/root/psa/PSA_7.5.2/rpm_RedHat_9/opt/vault/phpBook-1.50-7502.noarch.rpm
/root/psa/PSA_7.5.2/rpm_RedHat_9/opt/vault/phpBugTracker-1.19-7501.noarch.rpm
/root/psa/PSA_7.5.2/rpm_RedHat_9/opt/vault/phpDig-1.85-7501.noarch.rpm
/root/psa/PSA_7.5.2/rpm_RedHat_9/opt/vault/phpMoney-1.3-7505.noarch.rpm
/root/psa/PSA_7.5.2/rpm_RedHat_9/opt/vault/phpMyFamily-1.4.0-7501.noarch.rpm
/root/psa/PSA_7.5.2/rpm_RedHat_9/opt/vault/phpWiki-1.2-7508.noarch.rpm
/root/psa/PSA_7.5.2/rpm_RedHat_9/opt/vault/phpsurveyor-0.98-7506.noarch.rpm
This is a partial list from a RH 9 OS, Plesk 7.5.2 system.
So in this case, to get to where the files are:
cd /root/psa/PSA_7.5.2/rpm_RedHat_9/opt/vault
To install one of these rpm's, you would use the command:
rpm -Uvh name_of_file.rpm
But before doing this, you really need to go to the software author's site (not Plesk) and read their install instructions since you would not be using the App Vault module.
Their instructions may require additional steps such as copying the file to the domain's document root ~/domain.com/httpdocs before doing the rpm command.
Note: I am not responsibe if any of the previous info damages your system in any way. These work on my servers, and the admin has experience. You apparently are of limited Plesk or Linux experience and these instructions should be used solely for informational guideline purposes only.