One quick question first... Will this device ONLY be doing outbound communication? If it is bidirectional, then you will need a static translation and the appropriate inbound ACLs.
Otherwise, try the following ACLs on whatever interface is local to the device.
(This is an example you must insert your own ips)
access-list outbound_access extended permit esp host 192.168.1.1 host 1.1.1.1
access-list outbound_access extended permit udp host 192.168.1.1 host 1.1.1.1 eq 500
access-list outbound_access extended permit udp host 192.168.1.1 host 1.1.1.1 eq 4500
Pls rate if this helps