Yes, if making Aaliyah to Israel you are obligated (but not legally) to serve in the Israeli army - this goes for all citizens and permanent residents. That said, there's lots of get out of "jail" free cards. The best thing is to speak with a shaliach aaliyah about your case. You can be waved from service depending on your age, the case of prior visits, the duration of your planned stay, etc...
Obligation also varies for women and men. Basically, though if you arrive in Israel after the age of 20, service is voluntary - not mandatory. And if you arrive in Israel after the age of 26 - service isn't even an issue.
However, by other accounts, in reality you might meet with resistance from the army because of your age. I suggest you read through this blog and try posting your question there - http://aliyahsurvivalblog.wordpress.com/the-army/
All the rules for exemption of millitary sevvice today are the same as in the bible over 40yo people who grow a grove of olives and the scared and those who have found theyre bishert
Obligation also varies for women and men. Basically, though if you arrive in Israel after the age of 20, service is voluntary - not mandatory. And if you arrive in Israel after the age of 26 - service isn't even an issue.
According to this article on the Israeli Ministry of Foreign Affairs website (http://www.mfa.gov.il/MFA/Facts+About+Israel/State/THE+STATE-+Israel+Defense+Forces+-IDF-.htm) you can technically volunteer up to the age of 51.
However, by other accounts, in reality you might meet with resistance from the army because of your age. I suggest you read through this blog and try posting your question there - http://aliyahsurvivalblog.wordpress.com/the-army/