Hi, Telengo, and first of all welcome to the boards and of course to this great game!
Don't be afraid of Mac architecture. Once you've got used to it, you will wonder why you ever have done it any other way.
Yes, you're right that the current 1.72.2 test version (like all test versions) doesn't come with a couple of extras which were part of the latest official release 1.65. And it is completely safe to continue using the old extras. However, some of them have in the meantime been updated and are available on their own, like the
Oolite Reference Sheet, the Mac
ReadMe, and the useful
Oolite Keymapper.
And yes, the concept of "packages" is a little confusing at first. You may imagine a package like a folder which for the normal user, who isn't interested in the intestines of his software, appear like one single file. But opening its context menu (right-click on the "file") reveals its true nature, and lets you fiddle with its content, if you wish so.
A little warning: Usually you shouldn't do that, because if you for instance right-click on iPhoto and change contents inside the package, you are of course changing the program itself, which can be dangerous (in the worst case it could stop working altogether). Also as far as Oolite itself is concerned, we usually discourage changing anything inside it, if you don't know exactly what you're doing.
And usually it isn't necessary at all to fiddle with packages. iPhoto, to stay with that example, doesn't store files inside itself. Instead your photos go into a directory-structure within the "My Pictures"-directory. And preferences are stored under user/library/. And they can be changed (as can the default photo location) from within the application itself, while running iPhoto (usually preferences are available in the menu under the name of the program, therefore iPhoto/preferences...).
Anyway, as far as OXPs are concerned, I can perhaps tell you how I handle them: I've created a "Downloads" folder inside my main Oolite folder (the one where the Oolite-package resides next to "AddOns", "Pilots", "Extras" etc.). All downloaded OXPs go unchanged into this "Download" folder. The ones I like to install in my game I copy and paste into the "AddOns" folder. And then I can start to open and manipulate them to my liking. But the original in the "Download" folder stays untouched. So if I mess up anything in my personal copy, I can easily throw it away and restore the original, without having to download it again.
So the only thing left to say is: Have fun playing and fiddling!
Right On, Commander!
(And if you have any further questions, feel free to ask. You will very likely get an answer on this
Friendliest Board This Side Of Riedquat™.)