extras for the list ...
1. dependency list. before SQL2008 the sysdepends was incomplete but sys.sql_expression_dependencies should be ok. anyway, when you create that DEV environment try a simple SSMS script existing "with dependent objects" and apply to new temp DEV db. dependencies on target should be correct. usually produces compile fails of junk.
2. DMV to see what QP's are present in cache (i.e. some idea of what's [been] cooking)
3. DMV to see missing indexes (already noted), and busy/idle indexes (act accordingly)
4. Profiler. to identify users, [high] traffic and any deprecated stmts, recompiles, DDL
- but sparingly and don't capture what you haven't time to analyse!
5. if new box, consider changing audit failed AND success logins to see who connects
6. check users to see if still exist. suggest also part of the SSMS to temp DEV
7. logins ditto, checking for orphans. try sys.xp_revokelogin to temp/sandbox instance
+1 for DBCC
+1 for the xxx rename as easy to put back if crisis
- we used xmdd (eg x615) as datestamp to spot stuff could be dropped if 2 months unused (eg Aug15)