I struggle with the learning curve on Dorico, which seems steep to me. I’m on Dorico Elements 3.5. Sometimes I find online explanations of how to do something I’m trying to do in Dorico, but when I try to do it, it doesn’t work because it turns out that the instruction I read was for Pro, not Elements. I’m wondering if I got Pro if it might be easier to use than Elements. I don’t need the extra features. It would only make sense for me if the upgrade made things simpler, rather than just piling on more options that would actually make using it more complicated. I’d be interested in opinions, particularly from non-experts who have used both Elements and Pro, on whether it makes sense for me to drop $500 more or if that won’t address my issue.
I would certainly recommend upgrading to Elements 6. There are many improvements since v3. It’s £33 upgrade cost here in UK, so I guess ca. $45 for you?
You can request a free 60-day trial of each major version before buying it.
So, the best thing to do might be to get the Dorico Pro 6 trial, and test it out for yourself. You can switch between running Dorico as Pro vs Elements by holding the Alt / Option key down whilst Dorico starts up, meaning you can even compare the different varieties directly during your trial.
Online explanations (not to mention AI) are often either for the wrong version of the manual or are just plain wrong. At the very least, make sure to access the manual through your version of Dorico rather than searching on line.
It depends a little on what you mean by “easier”. In terms of general ease of use, I don’t think it would. There are more things you can do in Pro than in Elements, but Pro doesn’t change how you do any of the things which are available in both versions.
But there are very likely some things that require workarounds in Elements but which are available natively in Pro, so those things would be “easier”.
If buying the Dorico 6 license after the free trial, should you remove Dorico 3.5 Elements first, and is there anything you need to do to move over previous .dorico projects?
You don’t need to get rid of any previous version of Dorico for it to work flawlessly (I have Dorico 1 to 6 in my apps folder). Get rid of it only if you really need those 600 MB in your hard drive 
Any project created in a previous version will open nicely. Some changes might happen, especially with playback templates, so reapplying a current one solves the problem (that’s because our vsts get updated too, I no longer use NotePerformer 4 nor Pianoteq 6, but NotePerformer 5.1.2 and Pianoteq 9… YMMV). The Team has made great efforts to make sure files can be opened in different versions without issues (but the older versions will not display the newer features, of course. A cutaway score built in Dorico 6 will not display them in Dorico 5.)