i had quite a few very lose spokes on my rear wheel but it didn’t seem to be too far from running true, anyway i just tightened the spokes so they are all have the same tension (as best i can determine by feel)

the wheel still runs about the same maybe a slight wobble of a few mm, does this sound like it’s going to be okay or am i being naive to think it would be so easy?

well, the business of nipping up a few spokes isn’t that tricky, as you’ve found. 🙂
take a look at the sheldon brown website for a lot of info about wheel building etc.
might be worth using a SMALL amount of wicking threadlock on your nipples (on your wheels! ), so that they don’t come loose again, but do that only when you’ve got your wheel true properly, or at least to a point where you are happy. you can do this in the frame or fork as appropriate, using cable ties as truing guides, but take the tyre off so you can check the ’roundness’ of the wheel too.
it’s not a black art – though there is of course skill in building good, sound wheels quickly and efficiently, but if you follow the principles laid out by sheldon, it should be relatively straight-forward for a reasonably capable home-mechanic to adequately true a wheel and have it stay that way.

If the tension is high enough and even your wheel will not loosen.

If some spokes have loosened off it’s quite probable that the whole wheel should be re-tensioned.

i got the wheel built just before i went to france last year and never went back to get it re-tensioned after a couple of rides so maybe it’s just been “bedding in” over a years use on DH tracks