No, you should NOT take the update. And I'm surprised you even received it. That is not meant to come up when you're on a custom ROM.
If you want it, you need to flash the Google Images and start over, or just wait for the ROM to be updated and flash that.
Sprint HTC Evo 4G
Motorola Xoom WiFi
T-Mobile HTC G2
Quit signing contracts, stop overpaying for service, GO PREPAID!
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, and we both get more storage!