TOC - Internal or external
Thank you for all your comments and suggestions. I've been away from my computer so haven't been reading the forum.
I wish I'd asked my questions before I did all the work to remove the internal, hand-coded TOC from the files I used to create the Kindle version. The TOC is extensive as the publication consists of 5 books and I had to recode to make the naming of the different TOC levels consistent across the books. (Those who have not worked on the Kindle may not know that you cannot automatically generate the Kindle TOC, it has to be done manually. This meant that I had to hand-code about 1,000+ a-ref's and a-names)
My assumption that the TOC for the Mobipocket book HAD to be external was wrong. After reading just one statement in Harry's tutorial made me realize that I could have used the internal TOC. A real DUH! Thank you Harry!
I have now used the Kindle HTML with its internal hand-coded TOC to create the Mobipocket ebook. This allows me to provide links to each of the five books' table of contents at the beginning of the internal TOC so readers do not have to page through pages and pages of the table of Contents to find the TOC for a particular book. And I have used the Guides to take readers directly to the beginning of each book. A Guide also points to the beginning of the internal TOC.
I hope this description helps someone who may be working on a similar publication. If I'd read something like this when I began my project it would have saved me weeks of unneccesary work.