I get it, but my advice: do what you gotta do. It's not like the warranty sticker's intact. Do as many mods to this thing as possible if you think it's on the brink.
I still can't believe people still use those fan speed xex's xD I run my xenon modded xbox at 100% with 2 50mm fans. and my jasper at 70%.
well I would recommend replacing the thermal compound ASAP. Leaving the disintegrated garbage on there will kill your dev faster. Arctic silver works great. I had a xenon jtag that ran at 60 degrees when idling.. Thats pretty damn hot. After I cleaned the chips and the heatsink and added arctic silver 5 i was getting 35 degree temps when playing a FPS. After setting the fan speed to 100%.... Well the temps were in the 20's to say the least. Zephyrs are essentially a xenon with a hdmi port and a hana chip instead of the ANA chip.I doubt you need to replace your heatsinks, just the thermal paste will be sufficient.