Hi Dapper, I can answer a few questions. I dep'd in 2 months ago (20130403) and actually I was intending on signing for CTN but....there were no billets left and I was questioning if I had really wanted it or not.
1) I was worried about my ASVAB before going to MEPS and so I ended up doing a lot of practice questions but I was pretty much qualified for everything. Yes you can qualify. Specifically for CTN you need the following scores:
AR+2MK+GS = 222 (relatively high but doable). But you do not get the contract right away; you can get it the same day (most likely you will) but if you get held up a day or something like I did, you might miss the "jobs deadline" they have. For top security clearance jobs like the CT ratings, the liaisons have to get in contact with whoever screens the CT signers to give them a go ahead or not. I couldn't get the CTN job btw, no more slots left for it; at least by the time I went to sign and all.
2) Free time while in the Navy--thats a general question not exactly related to being a CTN. But with that top secret security clearance, I wouldn't imagine much.
3) CTN has one of the longest A Schools and also has some C schools I believe. I think this is a lot considering I think the rating sheet says its an accelerated course or something. Uhm but I guess you could try online college like in almost any other rating.
4) Chances; maybe pretty high considering you will have that TS Security Clearance and will possibly have been stationed at an NSA center as a CTN in the navy (they are "landlocked" sort of)
5) Since CTN was full for me, I picked CTM--I thought that was the next closest thing to CTN than the other ratings--but most people think CTR or CTT are I think. I'm thinking maybe I could do IT also. CTN sounds the most challenging though. What I'm second guessing about the CTM rating is I've heard its like being an ET with a TS Clearance--doesn't sound too interesting
I'm more of a computer/network guy. (btw got my Network+ certification today and have had my A+ for a year)