I've just realised I never updated my download after a mistake was discovered ages ago. Do I just download again and enter my original verification number?
That is correct. You should download and install in the same location. Just remember to not have the software open at the time of install. Normally you would not need to give the verification number. If you run into any trouble, just give us a call.
No, no, do not pay for the software again. Please use the link to download that was sent to you by email when you purchased the software. I will also send that to you via PM.