Welcome to the forum, Gentlehens.
Our wiki has a page on free ebooks:
https://wiki.mobileread.com/wiki/Free_eBooks
And on ebook lending libraries (remember: you don't necessarily have to live close to an ebook library):
https://wiki.mobileread.com/wiki/EBook_Lending_Libraries
(There's also a link to the front page of the wiki at the very top of this page.)
Your Kindle can read mobipocket format straight off, so you won't need to do any conversion.
You can also get free ebooks in mobipocket format from Manybooks:
http://manybooks.net/
and Munsey's:
http://www.munseys.com/site/home
The files you download will either have a .prc or .mobi file extension.
If you like, you could download mobipocket reader, then you could immediately download and read the books on your computer, while waiting for your Kindle to arrive. Here's a link from our wiki about mobipocket format:
https://wiki.mobileread.com/wiki/Mobipocket_Reader
Eventually, as you grow more confident, you can learn how to convert books from other formats. It's not difficult. When you're ready to have a go, then search the forums for advice, or post a query.