in uc 2 beta for d6, is related products type functionality built in? Do I just add a node reference cck field myself to the Product content type, then customize the node view for UC Product (although I don't see a node view for Product in my Views list, did it not get installed for some reason, or is there one?)
There isn't any built-in related product functionality. If you want to manually link products, what you posted would be the way to do it imo. There are other modules that will recommend content automatically, but they might not be worth the time it will take to setup.
Also, afaik there is no default View provided to override the products listing or the catalog. There is Views integration that will allow you to rebuild it, though.
the thing I didn't see in the views integration were how to get the product attributes data into my views, unless that is just thrown in with the add to cart form, which is probably the answer. I don't see how to get the Product images / images into a custom view, either, though. Any help is appreciated on this topic.
I'll see what I can figure out, thanks for the help.
I'll have to do some investigatin'. Could be the Views 2 integration just isn't complete. 
I think that Related Contend module is perfect for your needs.
I have used node refs in non-UC applications, and, by default, I think Drupal just pulls in the node id and title. I think you have to do extra work to load each extra node and get to its details, which in your case is the product with attributes.
I think this is a great spot for a module / addon, because if you have several related products and have to load all those nodes, it could get slow on a busy site.
Let us know if you find out differently.
UPDATE: After looking at the Related Content module, that looks like the answer for sure, I've never seen that one but it looks incredible, going to try it asap
Good luck 
By the way, yesterday I spent some time researching which solution is better for me to relate products. Related Content is nice but not so flexible as this solution
Hmm, you might also check out my Upsell module: http://drupal.org/project/uc_upsell - it's built for use in Ubercart pages, and in the 2.x version I'm going to improve the way the Add to Cart buttons work (allowing you to check the boxes of the products you'd like to add to cart along with the one you're looking at, along the same way Amazon uses.)
I'm not sure if the solutions mentioned in the threads above will scale very well, whereas mine should, although I'm looking at improving the codebase so scaling improves.
You can see the module in action on any RiffTrax page, like http://www.rifftrax.com/rifftrax/twilight. One of the nice things about the 6.x version of the module is the ability to base related products automatically based on taxonomy term. I'm testing it out now on our (soon to be live) D6 site and it works really well.
EDIT: Also looking at how Related Content works, I think it'd be trivial to create a mode such as "Relate by Node Type" in Upsell, alongside Related By Taxonomy. Actually this was something that John over at Acquia had suggested and I plan on putting in the 2.x of Upsell. That way you could have multiple "Related" blocks, creating kind of a "These products are accessories to the one you're looking at" type of system. Should be awesome once I get it done 

