Can we use a Paper Private Key that has been loaded in the Bitcoin client? Okay, I want to start offering Bitcoin as a payment option on my e-commerce site. For now, I just want to keep it simply as an option for those overseas customers who don't have credit cards/PayPal so I don't anticipate a high number of transactions. I have gone to Bitaddress.org to generate a bulk wallet, I have loaded the private keys (together with the related public address) on a USB drive and on an old non-networked computer. I plan to email a new Bitcoin address to each customer that wants to pay by Bitcoin. I have loaded a list of these addresses into bitcoinmonitor.net so once a customer pays I get an email notification after 4 confirmations and then I can ship out the product.   

2 Questions:  


How can I install Bitaddress.org on my non-networked computer so I can generate future paper keys without even being online, for added security? I know it's possible, but if anyone can help with a step by step would be great. 
I do have the regular Bitcoin client. Eventually I may want to consolidate all these coins into one wallet but still be secure. So I figured I could then import all these private keys into the wallet that is part of the Bitcoin client (using these steps https://en.bitcoin.it/wiki/How_to_import_private_keys_v7%2B). The question is does the private key somehow change upon import? To put it another way, if the computer which runs the Bitcoin client explodes, and I did not backup the wallet.dat file, am I still safe, because the private keys that are kept on my USB or even just written down can still be used? or did the action of importing the address somehow change the private key? If it is safe, I suppose there may still be a little loss of bitcoins if any "change" transactions created new addresses? Any help is appreciated (including any problems you see with my plan). I can't program (even html), but I am very excited about Bitcoin!
1.) The web page at BitAddress.org can be loaded from a file on a thumb drive or other storage.   Most browsers let you save the web page using a View Source (right click maybe), and then Save File to a thumb drive. 

Then from the offline computer you open the file from the browser and the BitAddress page will load.

2.) The private keys don't expire or invalidate after they've been imported into the client. You correctly identified the problem with that is how if you spent any of the incoming funds, the client creates a new address for "change" and thus the wallet may show a balance that includes funds not in any of the addresses from the imported private keys.  So wallet backups are still important.