First, make sure the box meets the HW requirements, especially in terms of RAM - most 515Es will have enough flash to upgrade to 7.0

Second, it's unfortunate, but you cannot just copy and paste the configs.

The biggest changes from version 6.x to 7.x revolve around 1) interface configuration, 2) VPNs & 3) modular policy framework (ICMP, fixup, etc.) 4) failover

The good news is that the inline upgrade, for the most part, works. Of those changes, the only element of config that may not properly be migrated after upgrading the box would be your VPN configuration - the move to tunnel groups and group policy is a big change and sometimes the ACLs used to identify interesting traffic for crypto maps does not populate properly. Upgrading is a great way to go - it even preserves the original configuration so that you can roll back, if necessary.

If you have a large number of site to site VPNs, I would lab test the upgrade before doing it in production. Really, that's just to get you used to the tunnel-group paradigm of VPN configuration.

If you are starting from scratch rather than upgrading, all of your object-groups, ACLs, names, NAT configuration and fixup data (though it will be transformed as you enter it ) can be copied and pasted directly. The interface configuration is more like that of traditional IOS and should be very easy to accomplish.

Conduits are bad - be sure to convert them to ACLs before attempting the upgrade.

Consider using the latest interim release if you run 7.2 instead of the GD release - lots of bugs have been addressed in the interim releases, some of which were pretty nasty.

Hope this helps - good luck!