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More than you wish you had to have, most definitely! Glad we could help!

I wouldn't use OSE for this, given that they may not crawl all your urls I suggest using a specifc cralwer that you can set to crawl the whole site. Give Xenu, Screaming frog or IIS toolkit a go to get a good idea of your urls. After you go live, make sure you have mapped all your old urls across to new ones In my experience, a site never actually looks like a tree, people just like to describe it that way because its simple S

If I am understanding correctly you want people to access DomainA.com when they go to DomainB.com? If this is the case, you could set up DomainB.com as a Domain Forward to DomainA.com. For instance a Client I have right now has www.drcharlescrane.com and www.drcharlescrane.net. Hosting is only set up for .com and we domain forward .net. You can also have this set up as a domain forwarding with mask so if you wanted the user would actually see in the URL domainb.com but pulling domaina.com's content. I hope this makes sense and if you need further clarification let me know. Also where is your domain registered. I use Godaddy primarily to the low costs for domains. Here is a how to domain forward provided by them and more information on the topic - http://help.godaddy.com/article/422