FWIW, we see people here all the time using customer-owned modems for the gigabit speed tier.
Hi there, neagle392.
Yes, you can use your own modem for gigabit speeds, and depending on the area you live, which is most now, you can do a self install yourself. Especially with you using your own modem.
If you have any other questions please let me know.
If you have any other questions or concerns, please feel free to reach out to us!
Thanks for being a Comcast customer!