Soon after I bought my vette in Feb of 2007, I discovered that my vette didn't have a thermostat! ad I was able to install a new thermostat and gasket with out draining the radiator fluid out. A little bit spilled out when we took the thermostat housing loose though, but it wasn't a big deal.
The Haynes manual says to drain the radiator. With all the paranoia surrounding the optispark system, you might consider that aspect of the job.
However, you can still do it yourself with an aluminum turkey roasting pan and the car's jack. If the pan wasn't previously used for roasting a turkey you can reuse the fluid that comes out.
The bigger question is, what temp of thermostat should you put in. I've heard numerous people say that a 160 is hot enough, but I tend to trust GM which puts in a 180 (I think) from the factory. Something to think about.
Most people do it because somebody else did it. Monkey see, monkey do. For certain racing applications, I can see the logic in it. A thermostat controls the minimal temperature range and the cooling fans control the upper temperature range of the cooling system. The LT1 was designed to run in the 190~195* range.I cannot understand why anyone would put in a lower temperature thermostat. It makes no sense whatsoever. Roger.