The motherboard (MB) is probably the most susceptible part to electrical damage due to the microvolts that it operates with.
Without your Dell service # or model # it's hard to check prices.  If you have access to another computer, you can check prices online.  Or have a friend do it for you, or visit your local school or library for computer access.
You can call/contact Dell with your service tag # and ask them what it would cost to have them replace the MB, assuming that they determine it is damaged.  Dell's website also allows you to see parts lists (get MB part #?) and may also show prices for replacement parts.  Installation not included in parts prices.  Ebay is a useful source for prices.  Check your pc model # or motherboard part/model # if you can, and search for that on ebay.  MB's seems to run from around $120-150 for Dells, and power supply $20-30.  You would then probably have to pay someone to install the part(s) for you.  
The hard drive/data is most likely fine.  The drive could be removed and placed as a slave in another computer to see if it can be read.  
You might be able to buy a used similar computer for less than the cost of repairs, or even buy a new computer today.  Lots of sales around just before the new school year begins.
Also, many/most? new computers are using the SATA internal cables to connect the hard drive, CD/DVD drives.  That may not be compatible with your old Dell hard drive which may be the older IDE/PATA which use a larger cable connector than SATA.  You would have to have someone transfer your files for you by installing your hard drive in another computer and then copying them over to the replacement computer.
..
Whatever you decide, consider spending $50-75 or more for a UPS (Uninterruptable Power Supply).  They are good for maybe 3-5 years or more, and are better at stopping voltage drops, spikes and surges than a $10 surge strip.  For best protection, the power as well as any other connections (LAN (network/router/modem) cable, phone line, or anything else connected to the pc should be routed through the UPS as well.  The manufacturers often provide coverage for replacement/repair  if your computer is properly connected and gets damaged from a surge.    One problem with low cost surge protectors/strips is that the MOVs can burn out with one good surge.  Some protectors have an indicator light that tells you whether or not it's functioning properly.
For more info, see http://electronics.howstuffworks.com/everyday-tech/surge-protector.htm

Paul Hachmeyer

-----Original Message-----
From: Personal Computer Hardware discussion List [mailto:[log in to unmask]] On Behalf Of Pete McMullen
Sent: Monday, August 15, 2011 5:33 PM
To: [log in to unmask]
Subject: Re: [PCBUILD] ZAP!!!

On 8/14/2011 12:44 PM, Michael Lanspa wrote:
> I'm just wondering if any of you would concur with DELL's diagnosis, 
> and if it is the motherboard and power source, would any of you have a 
> ballpark estimate on how much to replace them and whether our data on 
> the hard drive is still intact?
>

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