HP Laserjet 4000 and 4050 Maintenance Kit with fuser exchange -- This kit includes Genuine HP rollers and a brand new fuser.
HP's part number for a 4000 / 4050 maintenance kit: C4118-67909 (also C4118-69001).
Fuser exchanges: By purchasing a maintenance kit with a fuser exchange you are agreeing to send us your old fuser within 30 days of purchase. If we do not receive your defective fuser within 30 days we will contact you at the email or phone number given with the order. If the fuser core is not received within 45 days a $40 core charge will be issued to your credit card. Please send your defective fuser back in the box we sent along with the included return authorization sheet. Return shipping charges are your responsibility. The shipping address and return instructions are included in the box.
Here is a link
to our main site with all of the installation instructions.