SQLRNNR (7/31/2014)
In both cases, you can upgrade from 2000. I might even restore the database onto the 2008R2 box and leave it in compat 80 for a few weeks to test. Then switch compat to 2008R2 and continue to verify.
I don't know if upgrade advisor will check for old left joins such a *=.
But in our case we had old SQL code in ColdFusion & PHP, so even if the database itself is 2008 compatible, make sure any external code is also compatible.