63 Heater core

How do you remove the heater box under the pass side dash. I want to replace my heater core but can't get to it. Theres a bunch of clips that seem to be holding it to the firewall. Do I just bend these back with a screwdriver?
Thanks
[addsig]

Thanks Greg. Yeah, I have the shop manual but it's a 62 w/ 63 supplement. Apparently they thought that the 62 and 63 were similar enough that the 63 did'nt need it's own manual. I didn't realize until after I dropped $50 that it does'nt even cover my engine. It's OK for some things but worthless for other things, so sometimes I tend to refer to it last. Thanks again, though.
[addsig]