I would start with screws or L Brackets for your first time...make sure everything aligns...only use glue once you are happy with it...or for your first build just stay with screws and brackets.
As for your bezel. I wouldn't waste time using a jigsaw...go with a router.
Here is how I would recommend cutting your inner bezel.
1) Get the dimensions from your screen...place the screen in rough position and measure from inner side of cab to screen...top/bottom and side/side. Pencil those dimensions on to the MDF bezel (1/2" is good).
2) Use a router flush trim bit with top bearing and clamp MDF along the pencil lines like so:

Working from the top left to the right in a clockwise motion to keep your feed direction proper (outer edge you would go counter clockwise).
3) Use 3 pieces of MDF as per the picture...starting at top left go to the line i indicate on the picture and then reclamp and go to the next line.
Once you have done this you will have nice straight lined inner bezel. You can then use a 45 degree angle bit and mold the bezel at an angle so it creates the illusion of touching the screen etc.
Same applies to your sides...only the top side becomes your template that you run the router along...going counter clockwise this time. You clamp them both together...always leave a bit of over hang on the 2nd piece (bottom piece) so the flush trim can trim it. End result is that both pieces will be identical and line up properly.