10mbps is the conenction from your PC to the DSL modem, its way fast enough for DSL.
you could try a simple check like this one
http://www.firewallcheck.org/
or the one from
http://www.grc.com
If its a NAT based router you should be fine, your Pc's local IP address will be one of the non routable IP numbers, 10.0... 192.168.... etc