Hi Leenaud,
Well, it wasn't easy finding a guide specifically for your tablet; there seems to be a lot of confusion regarding model numbers when you toss in the "A" and "8.0" numbers, but I located what they're calling a teardown video. It shows pretty clearly how to get the battery out, but doesn't address the screen at all.
[link|https://www.youtube.com/watch?v=T8hMwA7DSpQ|Samsung Galaxy Tab A SM-T380 8.0" Full Disassembly Teardown Guide Screen Replacement - YouTube|new_window=true]
Now it says "screen replacement" but that would assume you've purchased the screen already mounted to the frame with the front glass. It's like the screen replacement on a lot of Samsung phones where the same sort of situation exists; it's possible to replace just the display, but generally accepted practice is to do the screen+frame assembly.
On the other hand, another video shows how to replace the front glass only if the LCD is still good. This one also shows removing the rear panel, but doesn't spend any time on the process of getting it off like the first video.
[link|https://www.youtube.com/watch?v=B3sf-B52x9k|Galaxy Tab A SM-T380 Screen glass replacement - YouTube|new_window=true]
Unfortunately I did not locate any guides showing how to separate the LCD from the frame if you need to replace that part, so hopefully that's not what you're looking to do, but it's not clear from your question.