A new reservoir coupled with an old print head or an old cleaning tray will not work out well. That said, you should not necessarily change the ink every time the printer complains about it. There might just be a simple problem such as dried ink in the jets on the print head, or ink that has seeped onto the copper contacts on the print head. Lift the cover. Remove each print head in sequence and check for ink that has seeped onto the copper contacts.
Instructions are in the manual.
Do this gently and carefully. Also check the copper contacts on the carriage. If everything looks clean, reinsert the head and move on to the next one. If any of those parts are dirty, clean off any ink using the special cleaning tools. There are pictographic instructions in the kit that show how to use the tools.