Upgrading Drupal

After working with the current versions a bunch for work lately, I'm interested in revisiting Drupal for a personal site. I dug up my old backup from when I took that site offline, and it's version 4.1.0. It does have some content that I'd be interested in keeping if possible, but I'm not sure the effort of stepping through the upgrade process will be worth it. Specifically, I had a gallery integration that we used around the time of the birth of our daughter that would be nice to keep.

I would like to upgrade my current Drupal 4.7 platform to Drupal 5.1, just wondering if there is proven or recommended path to follow.
I used flexinode for the 4.7 version. Is it upgradeable to Drupal 5.1's CCK through some tools?
For functional modules, will the table definition be different?
Your comment and assistance are appreciated!

What is the best way, if any, to convert a bunch of image nodes into a new cck node type with the main image as an image field?

Back in the old days of 4.6, before cck, it was often recommended to build e-commerce products out of image nodes /image/galleries. This was always a kludge, but it suited our purposes at the time. 3 years 1000 image nodes later and I would like to convert these into a more appropriate node type. After all, they are not images, they are products that include images.

I upgraded from 4.7 to 5 and now all the items in the administration menu are repeated twice. I saw a thread about this problem before, but I can't find it now. Please, could someone help or direct me to the old thread?

Is there an easy way to upgrade existing mysql 4.0.23 databases to mysql 5.0 databases?

Presumably one only needs to change a configuration setting once the databases have been translated in order to use the existng drupal installations (e.g. 4.7.6) with the upgraded mysql 5.0 databases?

I made a copy of a drupal 4.7 site in order to upgrade it to 5.1, The upgrade went fine and I now want to replace the 4.7 site with the new 5.1 version. The only problem is that since the 4.7 site was still live at least 50 new forum posts have been made that now need to be copied over to the 5.1 version.

Is there any easy way of doing this?

Also new nodes have been made on the 5.1 site so the node numbering will be different.