It all depends on what needs replacing and/or repairing Guy,
Normaly I find when I rebuild the likes of an MED 1380 it has only been fitted with a fixed duplex timing chain which does not alow for propper cam timing, if the milage and/or usage is high the main bearings will need a regrind.
Changing a cam is more involved than some people understand the valve springs have to be matched to the rising and falling rates of the cams ramp angels, the cylinder head valve sizes need to be mached the te cams inlet and exhaust durations and the compression ratio needs to be optimised to suite.
Generally a full rebuild to my Fast road Rally spec will work out at 500 euros labour + Parts and Machining
you can contact me for my information all my details are on my websight below
regards,
Paul.
http://hrengineering.webs.com