1st Please list them so we can give you some sort of answer.
2nd PICTURES.. nuff said??
3rd I have found that the various fora that are manufacture specific are the best starting locations. In the case of the S&W fora, it is populated by the SWCA. Smith & Wesson Collectors Association. As the posts are public they tent to be accurate. These guys can't afford to be seen as AH's by their peers.. The S&W site also has a forsale area where you can see what other people are asking.
www.smith-wessonforum.com
4th After you get a feel for the rarity and/or historical significances, you can search for a good home insurance specialty appraiser. These guys will put it in writing.
5th
www.gunbroker.com is one of the best auction site around. You can look at the sales history and get a good idea of the weapons worth. Remember to sort by the # of bids.
I do not collect, but I have a bunch of toys. Although none are "rare", several are on the hi-value list. In that they are over the 1K USD range.
Old does not mean rare, but in today's market, most weapons have significantly increased value.
Good Luck..
PS: DO NOT CLEAR NOR ATTEMPT TO FIX ANY WEAPONS WITH PROBLEMS. This will destroy historical $$ value..