I was going to fit a cartridge in mine when it went, but taking the turbo apart was almost impossible, 'cos the bearing/bushes had virtually gone, to say nothing of the carbon deposits and general ****e inside .. even though to look at it it looked perfect!! Worth taking the turbo apart and seeing how it goes first, I'd say .. though some refurb/new suppliers like a swap for the old one ..
I'd suggest a replacement 2nd hand turbo, a refurb or a new one ... and I love taking bits apart and fixing them, but it just ain't worth it in my experience.