Often it is much cheaper and easier to get life insurance a few years before you make your final decision and arrangements to move overseas.
When selecting health insurance ask whether the policy will cover you in your home country in case you have to return unexpectedly.
For more about insurance look at these leads:
1) Companies that have asked to be listed on Ask A Missionary:
http://www.missionaryhealth.com
http://www.globalhealthinsurance.com
http://www.gninsurance.com
http://www.missionaryinsurance.com
http://www.otpplan.com
http://www.talent-trust.com
http://www.GoMissionTrip.com
2) Web links and descriptions compiled by mission resources:
http://missionresources.com/insurance.html