Karin:
The file I get back from the photo lab is a TIF file - it is uncompressed. The resolution is 300 dots per inch which is print quality. As for color correction and quality, I am quite surprised at how close to the original the scan of the transparency often is. As with any print process, you strive to get it as close as you can, but it never completely matches the original. That said, the variance is not really that significant and I have been very satisfied with the results.
Mari:
Thank you for your kind words about my work.
My lab charges around $35 for a 4x5 transparency and around $55 for an 8x10.