Buying used is a risk all on it's own, so you have to do your own due diligence from that stand point alone before you decide to buy..
It's usually the appliances that will cost you the most for a TT.. Sure, if there are leaks and such, that can ruin a rig too, but that's gotta be part of the initial inspection to uncover..
Can't comment on the road service, as I've never had it and can change a tire if needed.. If the engine fails while on the road, I'll just call a tow truck and go from there... But, that's just me.
Bottom line is what will let you sleep at night?? Meaning, will you stay up all night worrying about what 'could' happen if you don't have the coverage, or will you stay up wondering if you'll recover your investment??
When I bought my TT 12 years ago, I opted OUT of the extended warranty that would have cost me #1200 for 5 years of extra coverage over the 2 year factory warranty it came with..
To date, nothing has failed appliance wise and the little things that I found along the way, I've taken care of myself. I've done a lot of my own "mods" along the way too, so i'm pretty confident in being able to do my own work as needed..
Good luck with the decision... You either "win", meaning you have so many problems with your rig that your "investment" pays off in repairs, but is that really "winning"?? I mean, if you have that many problems, it can't be a fun thing to deal with?? If you "lose", meaning, you don't have a single claim, but you didn't have any issues with your rig, at least you didn't have the headaches of all the repairs... :)
I feel I "won", because I didn't have any issues over the past 12 years and I didn't hand anyone $1200 in the process.. :)
Good luck!
Mitch