That's a nice machine you've got there Alex! It seems to be in really good shape for its age and 5883 hours isn't too bad either for it. I don't really see any signs of misuse or damage to the machine, outside of the work mother nature has done on the paint this machine seems pretty mechanically solid by the looks of it. That's also one of the newer 175's in the B series, I think that the 175 was switched to the C series shortly after 1981.
I might be off on the price of all the oils and filters but i think you could expect to pay somewhere around $300 for everything. I might be off, but its the best estimate i could make... i hope my young age doesn't make me way off.
Yes though about getting a bucket with teeth. Clay is a hell of a lot more difficult to dig with a general-purpose bucket and not only that, but you said you might be moving around some rock as well so a toothed bucket will come in handy there too. You should be okay with an in-line toothed bucket (meaning the teeth are all equal distances out from the front of the bucket edge).
Also, how about the engine? did you say you were going to use the one in there? or is it going to need to be replaced? If the one in there will work, could you tell me how it runs? Does the exhaust produce black smoke, or does it burn excessive oil? Check the levels and cleanliness of the transmission, hydraulic, and engine oil too. Those are also good signs of whether or not a machine is well taken care of. Finally, if at all possible, try doing some digging with it and make sure the steering and boom/crowd cylinders are tight. Then make sure that the engine doesn't get bogged down too easily when you are going into a pile or lifting the load up. Any other questions at all, feel free to ask =D
Logan