Yes, you can have a Messiah 2 installed. Your Neo 2.2 would have to be removed.
But,... how long has the Neo 2.2 been in that PS2 ? The damage to the laser may have already been done.
What version is your concole ? Go here if you don't know -
http://www.modchipshop.com/ps2/v5v6v7.htm