Lost Security answers

I am unable to log in to check my router to see if it is still working well. It gives me intermittant connections. Some days works greatr, then there is will be days with lots of waiting, or programs freeze and then return (on the TV while stremaing). The new printer had a hard time getting connected.  How can i get this checked.  Cox did a check and said it was a problem router and that I should sign  up for theirs (at $15.month) but I like the Netgear router.  I just want to know if it is working or going out.  I have purchased a new router, but if I don't need it I would like to return it.