Honestly, the printhead replacement isn't too hard if you're up for the job. You can use Canon's Printhead or an aftermarket one. I don't see a difference in performance. I have some links for some replacement printheads that fit your pixma. As far as disassembly goes, all you're just doing is removing the cartridges and the printer head that holds them, no teardowns.[br]
Honestly, the printhead replacement isn't too hard if you're up for the job. You can use Canon's Printhead or an aftermarket one. I don't see a difference in performance. I have some links for some replacement printheads that fit your pixma. As far as disassembly goes, all you're just doing is removing the cartridges and the printer head that holds them, no teardowns.[br]
[link|https://www.ebay.com/itm/QY6-0083-Printhead-fits-for-Canon-iP8720-iP8750-iP8780-MG7140-MG6310-MG7130-7740-/303388366673?_trksid=p2349526.m4383.l4275.c3#viTabs_0|Aftermarket printhead|new_window=true]
[link|https://www.ebay.com/itm/354211260808?epid=16034030377&hash=item5278a2e988:g:tx4AAOSwK9Fi8GIa&amdata=enc%3AAQAHAAAA4MZtTpWL9Jbl2lYMTENbH6B70bW%2FKNpim%2FBnt%2FxONf87MtzJi4NYY1h%2BE4SJQ73VyLQQtZsuDHXF31geqgBBR%2BYkvp1xlCA%2BA%2BV9pwYmKvAZy0gKS9XVDMHQElcch%2BC2qFBJ0EYSO2nAJcq59HTQMrOANAbkrUViJ0Td1DTgfQfwGpARSg19034TmjLJhRWgt6T9FPtusr0mFvpyHjPATFOZCn1RIN8udqmQuYOWfKCfJygkVgsk6A8wYJjR5yhs7krJmnYLWR1BtcTPFmxUuT%2FH5nGakqirjEMDIlI4S3aN%7Ctkp%3ABFBMrLC0l-1g|OEM Printhead|new_window=true]
Here's something from canon that shows you how to replace the printhead too
[link|https://support.usa.canon.com/kb/index?page=content&id=ART143853|Replace the Print Head On your PIXMA Series Printer|new_window=true]
And if you decide you really want to sell it, I would fix it up first, you'll get a better offer for it