Cisco backup route implementation.

Hello experts,

I require help regardinga cisco router backup route implementation.  Before i continue pls understand that my knowledge with cisco is limited.
I've attached the current config of our router.  Its a 2621. running ios 12.0
This is what we would liek to implement.  The current config works fine for incoming traffic on the specified ports.  All ips are nat'td to the corresponding internal ips.

I'd like to implement a backup via DSL using ppoe. Using the current router on a second interface.
 Firstly i'm not sure if i can even do that. Do i have to upgrade the ram and the ios? what would i need to do first.

Secondly, how would i configure the router with the same config as attacehd for the second interface via ppoe.

I only have one ip for for the DSL circuit. so i need to create port forwarding rules for the WAN ip to the internal network.  example. --  wanip:2311  ---> internal:2400

I'd like the second interface to take over if the link on the first interface goes down. will default traffic flow through the new gateway in this scenario?

I would really apprecaite someone having the patience to show me the config for the router.

thank you.

Current configuration:
!
version 12.0
service timestamps debug datetime
service timestamps log datetime
service password-encryption
service compress-config
!
!
logging buffered 4096 debugging
enable secret 5 $1$nkaz$UN0xamdfe6DSq2NED1o/
!
memory-size iomem 15
ip subnet-zero
no ip source-route
no ip finger
!
!
!
!
interface FastEthernet0/0
 description External Network
 ip address xx.xx.xx.xx 255.255.255.224
 ip access-group 101 in
 no ip directed-broadcast
 ip nat outside
 speed 10
 no cdp enable
!
interface FastEthernet0/1
 description Local LAN
 ip address 192.16.0.1 255.255.255.0
 no ip directed-broadcast
 ip nat inside
 no cdp enable
!
interface Ethernet1/0
 no ip address
 no ip directed-broadcast
 shutdown
 no cdp enable
!
ip nat inside source list 1 interface FastEthernet0/0 overload
ip nat inside source static 192.16.0.23  xx.xx.xx.83
ip nat inside source static 192.16.0.22  xx.xx.xx.82
ip nat inside source static 192.16.0.21  xx.xx.xx.81
ip nat inside source static 192.16.0.20  xx.xx.xx.80
ip nat inside source static 192.16.0.19  xx.xx.xx.79
ip nat inside source static 192.16.0.18  xx.xx.xx.78
ip nat inside source static 192.16.0.17  xx.xx.xx.77
ip nat inside source static 192.16.0.16  xx.xx.xx.76
ip nat inside source static 192.16.0.15  xx.xx.xx.75
ip nat inside source static 192.16.0.14  x x.xx.xx.74
ip nat inside source static 192.16.0.13  xx.xx.xx.73
ip nat inside source static 192.16.0.12  xx.xx.xx.72
ip nat inside source static 192.16.0.11  xx.xx.xx.71
ip nat inside source static 192.16.0.10  xx.xx.xx.70
ip classless
ip route 0.0.0.0 0.0.0.0 xx.xx.xx.94
no ip http server
!
access-list 1 deny   192.16.0.16
access-list 1 deny   192.16.0.17
access-list 1 deny   192.16.0.18
access-list 1 deny   192.16.0.19
access-list 1 deny   192.16.0.20
access-list 1 deny   192.16.0.21
access-list 1 deny   192.16.0.22
access-list 1 deny   192.16.0.23
access-list 1 deny   192.16.0.24
access-list 1 deny   192.16.0.10
access-list 1 deny   192.16.0.11
access-list 1 deny   192.16.0.12
access-list 1 deny   192.16.0.13
access-list 1 deny   192.16.0.14
access-list 1 deny   192.16.0.15
access-list 1 permit 192.16.0.0 0.0.255.255
access-list 101 permit tcp any any established
access-list 101 permit tcp any any eq 36865
access-list 101 permit tcp any any eq 5900
access-list 101 permit tcp any any telnet
no cdp run

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