Repointing a Stone Foundation

Hi there, I've been a lurker for a while on this great forum, but now in need of a specific DIY. Just purchased an 1890 3 family home which needs some random repointing of the stone foundation. There are spots of crack and there are spots where the mortar is missing. So I have a few questions to the experts... -Can I do this myself or should I get a professional? I have basic experience in DIY, but have never tackled something like this specifically. -What are the basic steps? Can I just chisel the old stuff out and slap on some mortar? -What kind of mortar do I need to use? Consistency should be fairly thick I assume?