The best-practice is to use whatever kernel that comes with your distribution-channels.
But if you're compiling your own, you certainly can use the old .config file for the basis of your new config. The tricky part is all the added modules between 2.6.27 and 2.6.32. The way I see it you have two options
Option 1: Do all the research
What's new in each kernel changes, of course. New drivers, new options on existing modules, deprecated options and modules change. These are documented in the kernel itself as well as in various other places. Some give a nice high-level overview, others are more bolts-level.
Option 2: Just go with defaults and recompile until you get something that works
make oldconfig with your old .config file copied into the kernel source directory and take all the default answers to all the new options. This assumes that new modules aren't likely to be critical for a system that was working on an older kernel. If this doesn't work the first time, it's time to go to option 1 and try again.