HSRP would be configured on the ISP side, not your side.
The switch will look and be configured like a single switch.
You will use the no switchport command on the two interfaces to the ISP. Each interface would be configured as a router interface and each would have an IP address. It will look something like this:
interface GigabitEthernet1/0/0 no switchport ip address 1.1.1.2 255.255.255.252 no ip redirects no ip unreachables no ip proxy-arp no cdp enable no shutdown!interface GigabitEthernet2/0/0 no switchport ip address 2.2.2.2 255.255.255.252 no ip redirects no ip unreachables no ip proxy-arp no cdp enable no shutdown!Since you are now considering using a port channel:
interface GigabitEthernet1/0/0 no switchport no ip address no ip redirects no ip unreachables no ip proxy-arp no cdp enable channel-group 1 mode on no shutdown!interface GigabitEthernet2/0/0 no switchport no ip address no ip redirects no ip unreachables no ip proxy-arp no cdp enable channel-group 1 mode on no shutdown!interface PortChannel1 no switchport ip address 1.1.1.2 255.255.255.252 no ip redirects no ip unreachables no ip proxy-arp no cdp enable no shutdown!Note:
You really should have a firewall between the ISP and your switch stack. Also, you can't use NAT on the switch, you would need a router for that.