sbd = soundboard
do your vocals go throught he amp too?
Yes.
you could try just getting the xlr -> 1/8" and give 'er a rip at home and see if that works. Does the XLR output say "line out"? I think you might have issues with the vocals and guitar not being mixed together well though. Maybe not though. And it will probably be mono.
If I understand you right you play in smal clubs by yourself with just a guitar and an amp with one mic running throught the same amp as the guitar, right?
if this is the case then what your outputting is mono anyway. try running the line out on the amp first. you probly wont like though. it's gonna sound hot, out of balance, and harsh. your only other option is gonna be to invest a little money in some audience recording gear. how much is up to you. you already hve the recorder so I'd work around that. an inexpensive single point stereo mic, a battery box and a small stand would probly run you around 100-200 bucks in the used market. you could do better but you'd be surprised at what a decent recording you can get with very little. you can obviously spend more but I'd think about weather or not you plan to persue this as a hobby outside of your own solo act or not. If so or if you plan to ever play with a full band a decent set of 'drum overhead mics ' (lux's, oktava, akg, or c-4's are all in the 200-400 dollar range for a pair) they will go a long way as field recording mics. but then you're gonna need phantom power and a pre.
start with the line out and see what you think.
+T for wanting to tape yourself...