1993 Sidekick 1.6 16 valve no start after head gasket replacement

[zukitrek]

Kick I have questions regarding head gasket replacement. My car runs superbly fine after the tune up (t-belt, WP, idler, new ignition system blah blah blah). I have not verified the reasons, but I loose coolant reservoir liquid after a month or so. I can see white smoke but only in the mornings and not every time. Car does not overheat whatsoever (so far) even in the hottest days here in summer. My question: Is that normal or maybe HG is failing and is being burnt in cylinders? If replacement is the route after verifying it is indeed HG, can I just do that with engine on car (20yrs without being opened)? of is a total rebuild a better option.

Thanks!!