I bought a rebuilt turbo from Turbos'r'us and it is already squealing on occasion at low speeds under zero boost with less than a few thousand miles on it. I don't know why. It makes plenty of boost and so far there is no smoke in the exhaust. My advice is Buy New and buy quality.
I am not a turbo expert, but I don't think you need to buy a whole new CHRA. I think a brand new genuine mitsu 16T CHRA could cost you more than a whole used 16T in nice condition. You can find a "rebuild kit" for much cheaper, around $60 I think, and keep/use the CHRA that you already have - which may solve your oil burning problem. Not sure how much oil your burning, but I would also look at your pcv (and all other intake piping) if you have the stock hose still circulating pre-turbo, as it could be as simple as your turbo is eating oil from the inlet. I would also search past threads, if you haven't already, to find out if there may be any other cheaper/easier to fix causes of burning oil. Would suck to spend lots of time and $$$ rebuilding your turbo, just to find you are still burning oil after it's all said and done.
There is plenty of info online about how to rebuild mitsu td04 turbo's, but you may want to bring your CHRA and rebuild kit to a shop near you to have them do it for you if that is indeed what you need.