Hi Albert,
Best post your enquires in the discovery forum.
Look for a copy of rave the land rover workshop manual for discoveries and read up on automatic gears box and transmission and you will find there are many reasons for the m& s lights to flash, like wise you will find detailed step by step instructions for removing and re fitting turbo etc and self levelling suspension information.
If rave is not available on this site, it is on D2Boysclub site.
As a first step to finding a solution to your problems it is worth having all your fault codes read( rather than jumping in and buying expensive parts ie xyz switch) and then posting a detailed description of the fault and its symptoms.
A couple of points to consider before changing xyz switch
The delay in moving away when you select drive when the m&s lights are flashing may be due to you being in 4th gear which is the default setting for the gear box
Known as limp home mode when the m&s lights flash.
If the m&s lights flash when starting the car it may be that the battery is faulty as the automatic transmission system is very voltage sensitive and a drop in voltage when cranking the engine with a poor batter is enough to register a fault.