Configure Router as AP with DHCP Enabled

Have an odd network:
DSL Modem has DHCP disabled, and cannot be enabled.
All wired clients have static IP addresses configured.

Need to add in a wireless router (configured as an Access Point) but am running into one issue:

I assigned the AP an IP address of 192.168.1.251.
When I enable DHCP, DHCP is giving out addresses in an appropriate range, but it forces a value of 192.168.1.251 for the default gateway. I'd like the Default Gateway to be 192.168.1.1 so that these devices can access the Internet. I can't find a location to change this.

This is a Linksys WRT54G2 v1 router.

I had it working at one point but we needed to update firmware and the backup configuration was corrupted.

Any thoughts?

OK, let me try rephrasing issue to see if this helps get a response to get me back up and running. I greatly appreciate any suggestions.

Existing network has no DHCP server. All clients are statically assigned.

I want to add in a wireless router and enable DHCP on it. I gave the router an IP address of 192.168.1.251 (same subnet as Default Gateway, 192.168.1.1). However, when laptops pick up an IP address they are being told the default gateway is 192.168.1.251, not 1.1.

Again, I had this working before a firmware upgrade, but am banging my head because I can't remember the configuration.

Many thanks for any help you can offer!