I don't know there are any examples out there of a 3rd arty successfully implementing a new user creation using the VB5 API.

Unfortunately if documentation and examples will be required (and I certainly understand why they would be expected) VB5 is not going to be for you.

Be aware that if purchased, once downloaded, no refunds will be offered.

I just googled and see some negative comments people complaining they get theme import errors when installing! Should I be afraid of this?

There is no yes or no blanket answer. Every users experience is different depending on their server/sites.

There were issues with improperly configured webhosts (in most cases). We've added work arounds for this.