Best way to crop it is by using FlaskMPEG. It has good cropping options, and it's simple to do. It's hard to explain it here, but there are thousands of guides on the Internet. Anyway, leave me a PM if you need some help.
If they're all the same bitrate, TMPGEnc is the software you need! It has a "MPEG Tools" Section with Muxing/Demuxing (mixing video+audio), MPEG Join & Cut. Go to File / Mpeg tools and choose [MPEG Join], load the files, put them in order, and TMPGEnc will do the rest.
If Not all the same bitrate, TMPGEnc won't work, so you'll have to use a Video Editing Software (like Vegas, Premiere, Ulead Video Studio) to put all mpeg's in a timeline and then render a new video.
Hope the info was useful. Greetings from Argentina!