coolant area ?, you mean into the radiator, or the resevoir tank ?
how much is a little extra ? a cup or two ?
thats nothing to worry about.
coolant is avail. as a premix or can be diluted in an empty bottle with 50% water and 50% coolant=50/50 solution.
repair information ?
You could try Pdfoo.com
5 pages of isuzu information.
Try this site,,www.4x4wire.com
isuzu repair info