Very time consuming. I'd say over 200 hours of playing. I'm in the process of doing this because I enjoy it. If you don't, don't do this achievements. It takes patience and you have to be organized. Write down all players you own so you won't buy them again. Don't pay more than 100 credits for bronze players. Don't pay more than 300 credits for silver, and don't overpay gold if you want to collect everything.
Includes the 5 countries, the 10 team other countries, all balls, boots, and stadiums.
Boots checklist http://www.xbox360achievements.org/f...ad.php?t=26071
Stadium checklist http://www.xbox360achievements.org/f...ad.php?t=25084