Jim makes a good point about the use of the M1841 by both sides in the ACW, but I have to disagree with his evaluation of condition. While it may lower the value on this particular example, it is NRA Antique VG condition and it is complete and "as issued", most collectors will be happy to have it as is.
For a good estimate of value, check Flayderman's Guide to Antique American Firearms and Their Values . Hopefully, when someone purchases it, they will do no more than wiping the iron/steel parts with an oily rag and preserve it as is. It is a good example that "saw the elephant".