GPU reflow soldering profile
A typical soldering profile for a semiconductor is as follows (this one is from an ST datasheet).



In addition to this, you must bake the part for 24 hours under nitrogen atmosphere.

That's for one particular part. To guarantee safety you must look up every part on the board and make sure that the profile does not violate any limits for each component (perhaps the part was originally attached manually after reflow). Since you also want this to work, you have to ensure the profile is adequate for whatever solder was originally used. A conveyorized oven with multiple zones is usually used to get the required short residence time at the peak temperature. 

In practice this is non-trivial, and for an attempted repair of something relatively cheap and where reliability is of little importance it is probably best to have at it with a nominal profile, perhaps shielding parts like through hole connectors and electrolytic capacitors  with aluminum foil if they are far from the suspect areas. Batteries should be removed.