Spend your money on Windows 10, not 8. I would spend money on new PC with 10, rather than trying to update and older one to 10.
You may find this post of interest https://accountants-community.intuit.com/questions/1871757-any-suggestions-for-a-replacement-for-pro....
It is your EFIN, so CONTROL IT "I dont know how to know how many efiled returns they are working" IS NOT AN ACCEPTABLE STATEMENT. You should already have their PTIN and have verified their license/credential allowing them to legally prepare returns.