I would follow https://www.google.com/webmasters/tools/change-address steps -
If you're planning to move your site
to a new domain, use the Change of
Address tool to tell Google about your
new URL. This will help us update our
index faster and smooth the transition
for your users.
For best results, follow these steps:
Set up the new site
Review our guidelines for moving your
site to a new domain. Set up your
content on your new domain, then make
sure all internal links point to the
new domain. Redirect all traffic from
the old site
Use a 301 redirect to permanently
redirect the pages on your old site to
your new site. This tells users and
search engines that your site has
permanently moved. Ask webmasters to
update their links to point to your
new domain and make sure incoming
links to your old site are redirected
correctly using the 301 redirects.
Add your new site to Webmaster Tools
Make sure you have added and verified
your new domain.
Tell us the URL of your new domain
Your account doesn't contain any sites
we can use for a change of address.
Add and verify the new site, then try
After submitting the change of
address, check your Webmaster Tools
data periodically to see if your new
site has been crawled and indexed (if
you have a Sitemap, one way to
determine this is by checking Sitemap
details for the new site to see how
many of the pages have been crawled
I would not presume that google will or will not sandbox it. Do you have sites / pages with google trust that you can link to if from? I suspect the reason I don't know that much about the sandbox is because I always link to new sites from established content. However, sandbox rules may vary on subject material.