Help needed! How to Play new games on my xbox. Please Help. Dashboard issues.

HEY! Alright, its gonna be a little long but PLEASE help me out, guys.
See the thing is that I got a Ntsc Xbox 360 from a shop where I live. They didn't tell me Exactly which Ntsc it was, or which lte or how they modded it. All they said was "it'll play copied games and you can buy copied games from us" . I being a noob with Xbox, bought it and didn't bother .. It was fine till the new kinect dashboards came out. With the new dashboard, as you all know, copied games don't work.
My problem is how do I play new games?
I got a Ntsc xbox so buying real games is pointless because where i live, they only sell PAL .. and the shops i used to buy don't sell fakes anymore.
I am sick of replaying AC II and splinter Cell conviction and other older games... I need new games.
My question is, HOW DO I GET THE NEW DASHBOARDS TO PLAY NEW GAMES... IS THERE ANY WAY AROUND IT SO I CAN PLAY GAMES LIKE AC BLACK FLAG OR AC 3 OR METAL GEAR ..ETC .. ???
I have Other shops ready to mod my xbox again for 70$ but .. I need to know.. if i give them this.. and they mod it and my dashboard is new and I can play new games.. will I be able to play my old games ? (ive heard you cant play games with the new hacked dashboards)
and IS THERE ACTUALLY A WAY TO HACK THE NEW dashboards or are they just lying to earn cash?
Thankyou for sticking. Your help will really appreciated. please Help me.. i need to know whether i should go ahead and pay them 70$ to mod it for new games .. problem is i dont know whether it will work ..

p.s- My xbox doesn't have the new dashboard.. it has the last dashboard where you can play fake games on. It's Kinect enabled but i can still play games.. I had a AC: brotherhood Cd, in desperation, i let it update to that dash but it didn't help.. AC: brotherhood still doesn't work. but Thankgod the rest of my old games do.