I have a quick question about installing the new Cyanogenmod rom. Would installing it over the current 7.1 rom without wiping data and cache work? Or would I have to do it every time I install a new one?
You can generally install CyanogenMod without wiping as long as you're within the same major release (i.e. 7.1 -> 7.2 is okay, 7.1 -> 9.0 would require a wipe to boot properly). Worst case is that you bootloop, usually, so you can always try it and then go back into recovery and wipe if it doesn't work. It's never caused problems for me before and I put nightlies on my devices on a fairly regular basis (2-3 times per week, usually).
The CyanogenMod team has also noted this in the past on their blog and in other places. The 7.1 announcement, for example, stated:
Upgrading from any previous CM-7 release or nightly build should be smooth and no wipe should be required.