Suite What's the best way to install replacing entire site?

[محروم.كوم]

I would like to install vb4 gold at www.officialbabyshowerguide.com. Can you recommend the steps I should take to install it and be able to move all the content into vb4 without the site going down until I've finished updating everything? I'm not very well versed on databases and such.

Is it possible to merge the users & posts from the php board with what I have just made at www.babysaleusa.com? For the record, I plan to remove vb4 from babysale and get rid of it all together.
If not, I guess I'll start the forum from scratch but I still need instructions above.
Thanks! __DEFINE_LIKE_SHARE__