I clicked on this thread because I wanted to know what L brakes were.
Assuming you're talking about cantilevers, then it's pretty straight forward to switch from one to the other because they use the same mounting bosses, but it will require replacing both brakes and levers, so the only inexpensive way to do it is to buy cheap parts
I think V brakes work great, and I've never had trouble setting them up, so I can't figure out why you'd want to switch. usually people are thinking about switching from cantis to V and not the other way round.