Note: I have to assume you mean the American short version of trillion (10^12), and not the international long version (10^18). If you meant the long version, I am sorry, but you'll have to correct the math yourself.
The posters are on the right lines.
Good and short article. I'll summarize it even further:
Temperature is related to the motion of the particles. The motion (speed) of the particles depends on their energy and their mass. If you could take the lightest possible particle and gave all the energy you could possibly give it, then its speed will approach the speed of light.
The planck's temperature is a reasonable approximation of that maximum temperature. At the planck's temperature, we can no longer see additional temperature increases, thus why bother considering higher temperatures? The temperature could exceed the Planck's temperature, but we'd never know it (the particle becomes a black hole).
Planck's temperature is 1.4*10^32 K.
The radiation heat question is even more complicated. Lets consider the case just before it is a black hole.
We need to know the black body properties of that particle (emissivity). That is, does the surface transmit all of the energy or does it absorb some of it? Assuming it is a perfect black body, then the energy it radiates per unit area is:
q/A = 5.67*10^-8 W/m^2K^4 * T^4 where T is the planck's temperature.
Thus, the body radiates 2*10^121 W/m^2 of energy. It would be really hard to maintain the temperature with this amount of energy radiating out of the body, but lets pretend we can do so.
Now, we just need to know the surface area of this black hole. The radius of a black hole is 2*G*M/c^2. Where G=6.67*10^-11 m^3/kg/s^2 and c is the speed of light. M is the mass of the particle, which unfortunately we do not know since mass increases with velocity. Rather than calculate it, I'll just assume the radius is 10^-15 meter. Someone else can come in and calculate that for me.
Thus, if the black hole is 10^-15 m in radius, the amount of heat it radiates is 2.7*10^92 W. At a trillion light years away, we would only receive a small fraction of that radiated energy. In fact, an adult human has only of 1 m^2 area (only half of the adult is facing this particle) and the heat radiating from the particle is passing through an area of 1*10^57 m^2 a trillion lightyears away. Thus, we only receive 1 W out of every 10^57 W radiated from the particle. Or, we'd each recieve 2.4*10^35 W of energy.
Since the sun gives the entire Earth 3.2 *10^13 W of energy, I'd say we'd be toast.
Note 2: Someone had better doublecheck my math.