Have you tried re-installing your network cards drivers? Also could try the Windows troubleshooter. Surprisingly, it does work and has fixed a couple problems I couldn't figure out.
Is your Dell still under warranty? Replacing the BIOS chip isn't just something you can do like replacing a RAM stick. You usually replace the motherboard if the BIOS is not repairable by a reset or re-install.
They have the same CPU and GPU, so either one should work fine. The J5 is the newer one but has less RAM and less internal storage space. I would say that either way you go would work, the A5 would just be a little bit faster.
What kind of laptop? Is it under warranty?
If you are not able to see anything on the screen but black, you might want to try hooking it up to an external monitor and see if you can get something to come up. Then run a diagnostic to see if anything is wrong.
Hey jeremyk, might try filling this out and posting it here. Will help others help you with your question.
http://www.tomsguide.com/forum/50797-35-laptop-buyers
I am so impatient. I went with the 7577 but got it from Dell as Certified Refurbished. Saved a little and have heard good things about their refurbish program.
If it isn't turning on, there may not be much you can do unless you are ok with taking it apart.
If it is still under warranty your best bet is to call Dell.