On my Dell Studio 1558, screen has several vertical lines from top to bottom: A couple of those on the very left of the screen and some others about 2 inches from the left border. They appear in different colors but most of those are white (means no video on the lines). But if I twist the whole screen (grabbing the top screen corners, pulling the right and pushing the left), all lines gone and screen looks good. Any idea? Still need to replace it?

no dear, there is no bypass jumper in it, go for the solution dell suggested for you

seems like your screen have some dead pixels. the only solution is replacing the screen. ita a hardware problem not software.

i see that the USB port is 2.0,and you need to upgrade your motherboard in order to use USB 3.0 device,and since it's a laptop,like what you said,it's very expensive

I would not consider replacing the motherboard, in fact Dell should be replacing the laptop for a design that does not have these heat related issues, I think if you made enough noise about this particular line they may replace what you have lost.

You can download the WEBcam abd device drivers from Dell WEB site,the support download page. Make sure you select your model desktop or laptop,better still, type in the Service Tag number, it is printed on the label on thebottom of the laptop and on the back or sides of a desktop. (If the Service Taglabel is missing then go into the BIOS setting and on one of the BIOS pages, theService Tag number will be displayed). This will open the page where thespecific drivers for your model computer are located. Also make sure you selectthe Windows of the drivers for your Windows operating system. Click on thislink to download the drivers: - http://support.dell.com/support/downloads/index.aspx?c=us&l=en&s=gen

Please get it replaced by a repair shop

Unfortunately the keyboard for laptops is not made to be serviced, the best option is have it replaced.

Here is the Dell service manual page where it shows the disassembling of the Dell 1558.
You will have to remove the DVD module to eject the DVD
Procedural steps are on this page site.

http://support.dell.com/support/edocs/systems/studio1558/en/index.htm

If the system is 2 months old, your best bet is Dell Tech Support as the system should be under warranty. If you hold the D Key and press the power button this should run the LCD BIST and you should get 4 solid colored screens. If you don't the LCD is bad. If you do, then the issue is likely the video card.