If the bake manifold is the only feature that does not work, your problem may be as simple as replacing the igniter. The following link explains:
http://www.fixya.com/support/r401858-replacing_oven_igniter_gas_range
Both manifolds in the oven are fed from the same gas source and regulator, and they each have their own igniter. If the broiler is working, its not a gas issue. The only other problem that can cause one manifold to fail and the other to light is a bad relay on the Electronic Oven Control (EOC) board. This is the clock assembly on the operator console. The igniter is a cheaper option and the more common fail item. I would recommend checking the igniter first.
Replacement igniters (if needed) can be purchased at any of the following websites:
searspartsdirect.com
appliancepartspros.com
pcappliancerepair.com
repairclinic.com
Prices vary between sites, so shop all of them for the best deal.
NOTE: If the connector plug on the replacement igniter you receive does not match the existing igniter, you should be instructed to cut the wires and splice them using ceramic wire lugs that should be included with the kit. Do not use standard wire lugs as they will melt. The ceramic lugs and the wiring to the igniter are heat resistant.
If you have any questions, or require additional assistance, please let me know. I hope this helps you.