There's a bit more to the rollover process
1) restore backup (where did you get it from)?
2) test new location for perf
3) set up automated backup for new location
4) lower TTL for DNS to minimum
5) after original TTL duration has passed, replace the old site with an "out of service" notice
6) run a backup
7) restore the backup on the new site
8) test the backup on the new site
9) switch DNS
10) return TTL to normal
Downtime will be after step 5 and should be only a few hours at most.