Wow - let's get this train back on the tracks!!!
Where are you heading to do your tec dives? I did my tec and trimix courses in Subic and La Union and went back a couple of years later to do my instructor. Who are ya diving with? I am so envious!!!
As for pre-requisites, you can look up the standards but I would suggest getting in as many dives in doubles during the process as possible. It's just a task loading and comfort thing. The absolute best thing you can do before going is make sure your recreational skills are rock solid and second nature. That way you're not over tasked when they start throwing shutdown drills in neutral buoyancy and stuff like that at ya.
Did I mention I am envious?