you can hire blue badge guides (accredited + trained guides) for personal visits - try Tourist Information centre, Sea Terminal, Douglas (look up via www.gov.im)
You can hire cars - Tosaby (just to east of Stony mountain and 2km north of St Marks can be reached via bus (route #4) but is a good walk from Eairy Dam to reach the farm - most cemeteries are reachable by public transport - probably those of interest would be St Marks (a small yard), Kk Patrick and the very large Malew - a visit to Manx Museum Library (open Tues thru Sat 10am-5pm) would be advisable to get plans of yards + location of specific graves - not all churches on Island are open all day - the Museum library also hold most if not all original parish registers + other documents.