Re emigration - have a look at http://www.isle-of-man.com/manxnotebook/famhist/genealgy/emig.htm
Re getting a guide - have you tried the relevant department off the gov web site www.gov.im - there are many 'blue badge' guides.
St Marks is in South of Island, a couple of miles from Ballasalla (ie not far from Airport), but is not well served by public transport so you will almost certainly need private transport; car hire is easy on the Island but if it is your first time driving on the left, then the narrow roads of the Island might not be your best place to start, especially if the Manx weather turns against you. Distances are short but allow more time than you might expect.
Get yourself a copy of the Ordnance Survey Landranger map 97 which covers the Island and plan what you want to visit - towns such as Castletown, Douglas, Peel etc are well served by public transport but the areas off the main roads are not. If you are looking for specific graves for example check out the IoM Fam history MI's (eg at Manx Museum) for ground plan of yard - St Marks is small but others are much bigger and you can waste much time in searching