Totally Bamboozled!

Hello & I apologize in advance for my ignorance.
Have just completed a new site, registered with Google & wanted to add a sitemap.

Ummmmmm…suspect I’m doing something wrong, as I’ve tried to use your wonderful SiteMapGenerator a couple of times, but it seems to be crawling for hours with thousands upon thousands of lines………and no sign of stopping

I’m confused about it all – worried I’ll "damage" my submission with Google by over-supplying (?)……..

I have tried to find info about all of this, but am over bamboozled by the amount of info out there – so thus very confused!

sorry if off topic: Also confused about robots.txt – is essential? or not? excluded files, and so on,
(so yes – I am very sorry for my ignorance – but I’m really at a loss……)

Thank you