This is KB19372 with the SRX example configuration for GRE over IPSEC
http://kb.juniper.net/InfoCenter/index?page=content&id=KB19372
You will use the gr-0/0/0 interface for the GRE tunnel terminiations.
You do not need the PIC warnings are these are likely from the MX configuration examples which has a different hardware architecture from the SRX.
the GRE tunnel endpoints do need ip addresses assigned and the routes to those remote side ip addresses will be throught the IPSEC tunnel interface.
The routes to the remote GRE subnets will be to the local gr-0/0/0 interface for that tunnel.