You can find a partner or buy installation support from Xandros to be sure.. But you are on the right track.
I would install te updated scalix connector first for a newer connector can talk to an older server and not the other way around. In the admin guide you can find how to auto-upgrade the connector.
If you run the scalix-installer it "just" upgrades everything _but_ i don't have any experience skipping versions in scalix upgrades..
please review the releasenotes