its not the best just to change lifters on a worn cam as it will just mash them up and mince the lobes on cam shaft. get a piper / kent / newman cam kit. might cost 200-300 but to be honest its the best way to go.

as for blue smoke start off by changing the stem seals, cheap and easy to do with the tool. you can make a tool using a old spanner, drill a hole in middle and bolt it to rocker stud, use a lever to push spring down to get collets out.

whip the down pipe off turn and check if its full of oil. that will tell you if its hot oil seal on turbo. Also check breather pipes are not full of crap/ oil.

but id say if the engine is chewing lifters up and has a fecked cam, remove engine and strip down for full inspection and fit new cam and a new set of rings and all new gaskets/ water pump and oil pump. then you know everything is good. then you will have full peace of mind and the cvh is piss easy to work on.