Do I need to "unroot" my Evo 3D to get the ICS update? Android 4.0 just came out for my phone today (a Sprint-version HTC Evo 3D). I didn't get the update yet, but I guess Sprint is doing it in phases. Anyway, I'm wondering whether I need to unroot my phone before installing the update. I used HTC's method to root it.

Another thing I should mention is that I currently do not have the ability to install "Firmware updates" from the "System Updates" settings menu. There is a pending update now (not the ICS update), but when I try to install it, the phone restarts, then shows an error (what seems to be a green robot with a triangular warning sign above).

Does this mean I need to unroot before installing any firmware updates? If so, how can I unroot it, when it still has HTC's bootloader?

I am aware that there are ICS ROMs I can download and install, but these all have problems, and I'd rather stick with the update from HTC. What do you guys think I can do?
ROM Updates from vendors/manufacturers/carriers usually evaluate checksums of at least the system partition -- which fails in case of applied modifications, such as required by rooting (rooting needs to place at least the superuser apk on the system partition, and other root-apps may then add to it). I'm not sure how this is handĺed by HTC for devices "unlocked" via their "service" -- but in all cases I experienced, OTA-Updates failed due to the CRC check.

"Un-rooting" will probably not help much: the system partition remains "tainted". The only thing I know which should definitely help is flashing the original ROM locally.

As for me, I ended up using CyanogenMod on my devices, which runs quite smoothly (HTC Buzz as well as Motorola Droid 2). If you either have to flash (the original stock ROM), you might want to give CM a try. A good backup with Titanium Backup should take care for your data and make migration easier.