tbh mate it doesnt look that bad like jake said i had mine re conditioned, they also ported and polished the inside of the casing! mine has them type of cracks around the wastegate hole and he said its just the way that the casing is made it wont effect anything, unless the cracks are really deep and look like they might actually split the casing i wouldnt worry! however it probably is worth £200 to get the turbo over hauled before going through all the time effort and money included to get the turbo on your car (gaskets, new oil, bolts etc wateva else you may need to do the conversion!) that way you know you are working with a 'new turbo' as opposed to one you dont know how much life is left in it!
hope everything goes well for you mate need any help with the conversion just pm as ive had mine off a few times befor e now lol!
also consider the option of 'hybrid' the turbo especially if you do go down the route of having it reconditioned! i only paid an extra £100 for the hybrid and it will mean you get better gains! i know i certainly did.
dave.