This is a user to user forum so we can't check tags. (Tags should not be posted in the forum) All in ones have integrated video and everything else too. The motherboard on a AIO is like a laptop board. When something goes bad most of the time it means replacing the computer if you are out of warranty. Like a laptop aio has a shorter life span. Yours is 5 yr old model so you should consider a new computer.
You don't mention what happened with the external monitor. I assume it didn't work.
Some all in ones don't have a video out hdmi port, check your manual to make sure you have and use the right HDMI out port to attach an ext monitor.
Here are the stats for 9020 aio-