If you want to migrate your servers over (for prefs, see below) to the new package, do the following:

1) Install AndChat and BUT DO NOT OPEN YET:
2) Open adb shell and do the following:

cd /data/data/net.androidirc.irc/databases
sqlite3 irc.db
.output /sdcard/irc.sql 
.dump
.exit

cd /data/data/net.andchat/databases
sqlite3 irc.db
.read /sdcard/irc.sql
.exit

Now open app. It will do an db upgrade for charset support. If all goes well, you should be able to use the same server profiles without issues.

Migrating preferences:

Open app, close it and do the following in adb shell

1) cd /data/data/net.andchat/shared_prefs
2) cp /data/data/net.androidirc.irc/shared_prefs/net.androidirc.irc_preferences.xml net.andchat_preferences.xml
3) ls -l ..

You'll see an output like the following, note the ID down:
drwxrwx--x    1 10053    10053        2048 Nov 11 22:16 databases 
#ID = 10053, we need the part after 100, in this case 53

4) chown app_53.app_53 net.andchat_preferences.xml
5) Open app and confirm you still have your old settings.