> By the way, is there a wai to select hidden edge or face or anything else without have to switch on and off the other objects?
With the cursor over what is hidden, hold the left mouse button down and a window pops up with a list of hidden entities.
Moving the cursor over each in the list will highlight them; select the one you want.
For your main issue, I've found using joints to be very nice; I suggest you look at the tutorials.
After you create the joint you can right-click to edit, but that doesn't work a lot of times because components can scatter all over from their actual current positionss.
MUCH better is to use Modify/Change parameters to bring up a list of parameters (dimensions).
You can change the entries for the joint (many you won't have actually entered, they will have defaulted to 0), hit enter, and they update on the screen right then without having to exit the form.
Also note that X/Y/Z for joints are per the joint symbol coordinate system, not origins in the scene.
You can play with the entries until you get what you want.