LAMS CAP411 is not currently available for download from the CAA web site and has to be bought from documedia.
As for the engineer, it does not have to be via a maintenance organisation for a private cat a/c but you will need an engineer(s) licenced AND type rated in the appropriate categories (A/C and R)
A visit to your local M3 maintenance company should secure you a copy of the LAMS worksheets.
Beware, if you are new to the a/c make sure you research it's history and don't get caught out with any inspections or overhauls due. Extensive cross reference to FAA AD's (if of US origin) and manufacturers SB's will need to be carried out which is why it may still be best to go via a maintenance organisation, where they will have all the pertinant information to hand.