Let me help a bit with backplate removal process. This is from my old guide.
To remove backplate you will need credit card type plastic, any plastic card will do, no metal to touch motherboard!
Here is backplate. I used as you can see 4 peaces of plastic folded in half, approximate size (width) of already folded plastic is about 1-1.5 centimeters wide and 4-5 centimeters long. First you have to use plastic card (library card, credit card or similar) to lift backplate up a bit to insert those plastic assistants. Backplate is glued to motherboard! As soon as you inserted those FOLDED plastics, you can stick regular, flat screwdriver into the plastic folds and now you can use more force to lift backplate off motherboard, there is no rush here, you might need about 1 hour of monkey job. Lift a bit on 1 side, advance plastic closer to center, move to another corner, and so on. MAKE SURE THAT NO METAL TOUCHES MOTHERBOARD!Upper left corner on my picture is the most difficult to insert plastic and lift backplate, be extra careful here - there are a lot of protruding parts in this location.
The glue, sticky paper located on the outer sides of backplate square as you can see in next picture
As soon as backplate is out, you have to carefully remove this sticky paper, here you can use only you fingers and nails - no metal here as you can easily scratch motherboard, improvise.
Just another 2 cents.
Absolutely forgot.
This is Zalman
Backplate looks like the Dell one, so should fit, as lond as distance between holes is the same.