(1) What should I do if they insist on returning the current system back before they give me the new one ?
(2) Also how would I know whether the new system is not a totally new but it is the same one that I have & they just repaired it & gave me back ? If that happens, what can I do ?
(1) If they won't give you the satisfaction, and assuming you are in the United States, send out a hardcopy
letter to Dell and CC it to the Consumer Product Safety Commission and the FCC, explaining in two paragraphs or less that you are receiving repeated electric shocks from the front panel, but not the chassis, of a system that is connected to properly grounded 120V residential outlet, and that you would like this system replaced immediately, as you believe it may be emitting harmful electric potential and EMI/RFI due to a faulty or unapproved design. No threats, no ego, and no fifteen paragraphs of angst and frustration -- just a few brief, plain statements describing the problem and the desired resolution. Send all three copies to the appropriate complaint addresses using certified mail with a signature-required option.
This bit of performance art will cost you about ten bucks, but it sounds like you have a legitimate cause of action -- and if you don't have a replacement system on your doorstep in four days, there isn't much else that will do the trick.
(2) If it comes to that, why would you care, so long as it works correctly?