Reviews on the 870 are dated 2000. So if it is that old it has done sterling service. Fairly sure that the print head is built in so no replacement of it possible.
Problem with replacement is the infrequent use and stored in cupboard meaning that if it is an inkjet then the inks are likely to dry up/clog due to non-use and result in frequent cleaning. Incidentally is this the cause of your problem?
What colour printing do you do? If photos perhaps use an online photo printing service instead and not buy a printer.