A managed switch is only used for working with network traffic. ie creating network segments with different VLAN's, prioritising network traffic from/to specific devices by using QoS. I work for a large MSP and of all the people that work within my teams, maybe only 2 that use managed switches in their home set up. why? because they can, they have the knowledge and can configure them, however, this is only due to the inner geek and not actually due to the requirement.
I run a few 5 port TP-Link switches in my house that all connect into my Netgear x10 in my home office with my Hub4 in modem mode. I run 10Gbe on my home PC because the x10 has a 10Gbe port as does my QNAP NAS, again, its due to the inner geek and not due to the requirement.
If you are not going to be segregating traffic or prioritising bandwidth for devices then a simple dumb switch will see you right. As for the router, that's going to be down to the requirement again. If you don't need specifics that the VM equipment cant do, then no need to change that out either. Depending if you are within your returns period, you might want to look at that route to ensure you get 100% of your cash back rather than taking a loss selling it.