Operation was a success , managed to get the original seal head out in one piece(figuratively....well 3 pieces I think they are), filled with 500ml of oil 5w-20w shock stuff and gassed with 200psi plus of plain air just with my racing bike hand pump straight onto the hypodermic needle. Seems to be working well, seal head has a recess and circlip can be wormed out by rotating with some multigrips, then the second has to be removed before pulling the plunger out.
The oil was fed with the reservoir at the lowest point and tapped frequently to get out trapped air ...filled to between the circlip retainer grooves, piston in reservoir was set at about 30% from the top, second circlip was not refitted as this hinders the insertion of seal head which is actually pushed slightly passed this point in aid of easy fitting of the last clip, the needle is left in valve to facilitate air escape during the process, then pumped to desired pressure once clip is installed.
Total cost for exercise was nil $ as I already had the oil leftover from a previous job...however I was stung $17 for the initial regass at the shop which only proved to serve I had insufficient oil in the shock to begin with ...hope this helps someone with their shock
and thanks to all for their input