Once you have the Regiment, much of the battle is over. The reason I suggested joining the Yahoo Groups is that many members, such as myself, have access to personal archives.I paid a friend over $2000 to obtain photocopies of over 2000 pages of material . . . so when someone asks a question where the answer is in that material, I don't have to go to the PRO to check it out . . . I have a copy at home ( in the U.S). Other members have similar records on other regiments. If you pose the question and nobody knows, then you may be stuck paying a professional researcher (unless you want to go to the PRO yourself---but the least expensive option is to pay someone who knows what he/she is doing to check it out . . . but it could take the better part of a day at $30 to $50 per hour)
Give the Crimean War discussion group a shot first . . . and/or query other genealogical sites . . . If the obit mentions age, dob, place of birth, etc. you might be able to get some help at an LDS genealogical research center.