Welcome to Justanswer.com, my name is Dustin.I'm sorry to hear about the issue you are having, I will do my best to help you resolve it.
I find the best thing you can do when replacing parts on those machines, especially considering how many parts there are.. is to refer to the field service manual.
If you dont have one, you can download one for under 10$ here http://www.qmanual.com/printer/konica-minolta-1/minolta/konica-minolta-minolta-di250-field-service-service-manual.html
Its a solid investment, and will show you step by step how to remove the drum, and how to replace it. And then how to reset the drum counters afterwords.
If you have further questions, let me know.
I strive to provide great service, and greatly appreciate a 5 star rating clicked and submitted when you are satisfied.. I always answer follow up questions.Dustin S.Senior Technician and Network Switching Systems Operator / Maintainer.