I know what you mean about 'getting on' and the people you relied upon not being around any more. ;-)
Provided it's the same kind of suite, Total Protection in your case, I see no problem simply installing over the top.
The product key entry system is simple.
You can activate your CD key from http://www.mcafee.com/mtp/retailcard
Go to the website and choose the country and enter the CD key
Click on Submit and follow the on screen instruction to activate the product.
Once it completed you can un-install and re-install the product from your McAfee account online.
If you ever need to uninstall the procedure is laid out here: http://service.mcafee.com/FAQDocument.aspx?lc=1033&id=TS101331
Technical Support is always available free of charge via phone or online chat through the link under 'Useful Links' at the top of this page, as is Customer Service (for any account questions).