Q126a
For the CA ninja, it says that sudden strike damage is treated as sneak attack damage when qualifying for feats. Would this include the benefits of the Telling Blow feat from PHBII? ie. If I land a critical hit, do I get to apply my sudden strike damage even if the opponent is not denied it's dex bonus?
Yes. If something says Sneak Attack, you can use your Sudden Strike instead of or in addition to your Sneak Attack.
Q126b
For sudden strike it states that you cannot use it on a creature whose vitals are out of reach. Could you, with a level 7 ninja, use speed climb to ascend an enemy to a point where their vitals are in reach, strike, and then use wall jumper skill trick to jump away from the beast and back to ground. (assuming that it was within your movement limit)
Generally speaking, this is not necessary. If any square of a creature's space is within your reach, their vitals are within reach. Striking at extremities generally refers to fighting creatures like
Krakens with absurd reach numbers, where you ready an action to hit their tentacle as they attack in order to try and disable their natural attacks. There really aren't any rules for this written. If you need to climb up a monster and hit it in the head to strike a vital point, then you're already in the houserules territory and should consult your DM. What you propose sounds very reasonable with Spring Attack, but if you don't have that feat then you'd likely climb up, stab, and then be stuck there on the enemy's turn. Also, you're almost certainly going to have to enter the creature's space in order to do this, which would provoke an AoO.
Q127
I've heard people refer to overcoming immunities to sneak attack damage, but they never seem to reference where it is from. Can you please let me know what spell or ability or whatever would allow someone to overcome such immunities? Or what book I would read about it?
There are a lot. The most obvious are Gravestrike, Golemstrike, and Vinestrike. They were originally printed in CAv, but I don't think they actually got re-printed in SC. Wands of these spells are cheap and useful, as they're all first level and, thanks to Rules Compendium, activate as Swift actions. The Wand Bracelet in MiC is like a Glove of Storing on steroids and will allow you to keep these items at the ready.
Sorry, I'm kinda noobish. I've kinda been out of DnD since elf was a class, not a race.
Dude... I remember playing an Elf when I was... 12? Was pretty awesome.