Crawl underneath the back (!) and see if you have the large tin under-tray still attached. If you have, you`ll see nowt, if you havn`t then look for the exhaust header pipe on the left, where it runs back towards the front of the van, it`ll bend round back on itself, where it bolts to a rusty looking lump, that is the turbo. The other end of the turbo is alloy and will have a black rubber/plastic hose attached to it.
Cost-wise, expect £300 - £400 for an exchange/re-condition unit, plus fitting, which can take anywhere between an hour and a day, depending on whether the bolts holding the turbo to the manifold come undone, and if the rusty nuts holding the exhaust header pipe to the turbo come undone (not much chance of that) or shear off at the turbo (lotsa chance of that)
If you are doing it yourself, make sure you use a BRAND NEW 12mm double-hexagon socket (a good quaility one) to undo the 4 bolts holding the turbo to the manifold, if you chew those heads up you`ll be in a world of pain

Keep it real.
Search first - ask second ;>}