Yes, this is very easy to do. You can find instructions how to replace a laptop screen and both glossy Acer Extensa 4620 screen and matte Acer Extensa 4620 LCD display on NotebookScreen.eu

Based on what information is on www.notebookscreen.eu the only screen size for this Sony Vaio VGN-FW465J laptop is this original screen. If you have issues with your screen, you can get cheap replacement screen for Sony VGN-FW465J laptop LCD. Technically your laptop can support FullHD, but 16.4" LCDs are only for Sony laptops, and since they don't make laptops with that screen, you won't have an option for it :( 2CCFLs are providing brighter backlight, but consumes more energy. Your laptop only has 1 CCFL.