I'm in the middle, early stages of an R&R. I've removed the stock radiator. It was a bit more difficult than expected. There are three 7mm screws on each side connecting the upper shroud to lower - very hard to access. When I put it back together I'll reverse them and install from the inside for easier access (I read that suggestion in other discussions).
Not surprisingly, there was a lot of dirt and junk in there. I could probably clean and reinstall the stock radiator, but I'd rather not do this job again, so I'm ordering a Dewitts.
As with most of these projects, it's growing. I ordered a set of hoses and a t-stat from Jerry's Gaskets, a "Big Mouth" air dam*, and I'll be adding a screen to help keep out leaves and junk.
To answer your question, I do think you could do the job in a day or weekend (or two nights). If it has never been out and cleaned, I'd think it will be very worthwhile before your track event.
*
http://www.c4orcecorvette.com/