Unless you are scanning the pages in yourself you don't need to worry too much. Just use a program like 7zip to extract the images from where ever you've downloaded your comic from.
For irfanview batch conversation there are many options, but because the X7 resamples it's not really important. Often you'll find comics in either jpeg or png. If in jpeg you don't need to convert at all, just copy the folder to your X7 (not just the files, but the folder itself). If it's in png I think the default setting is to convert to jpeg, but if you click options you can make sure it is the maximum quality if you want. So to make it simple: open one of the images in irfanview, click file 'batch conversion' it should show in a new window all the images you've got in the folder with the image you opened. Click 'add all' and then choose a destination folder (I usually just tell it to make a new folder within the original folder), then click start.
Hope that helps. There's as many different kinds of comics as there are kinds of music, so make sure you choose something appropriate to your age and interests. It's not just for kids esp. if you're willing to try manga