buying a used turbo is a GREAT idea, to really get the car moving, but when buying anything used be really carefull, or you may get burnt badly (broken or missing parts, or no parts at all.. lol) luckily that would not be the case here.. im SURE he is very reliable... (how much are you asking for the turbo anyway.. and what does it come with..
and beyound that i have the same motor as you and i have sprayed it with nitrous for a little over a year now.. works great. i would honestly pick some type of forced induction and go with that, then dick around with the little stuff, but if he is leeting the turbo go for any amount in your budget i think that would be a great start...

ps.. i would consider a swap later.. see what you can do with what you got, you said you are new.. so i would not advise sinking a lot of cash into a new motor when you are not that knowledgable about this stuff... and swaps can get pretty pricey ..

is the car stick or auto???