Broken down engine

I have a nissan navara 91 model its done 360 000 k'sbut its a 4 cyclender 2.4litre petrol 2wd I was drivin today and as soon as I got to second gear the car just sorta died it lurched like I hit the braks and then it would run for about 10 secs and stall the engin runs extrealmy rough skaing the hole car its not feul and I just did a service on and the new plugs have a small rust ring on them as water is in it it spits out white smoke and I had to get it towed ome I have taken the rocker cover off and there is roack hard cooked oil form a long time ago but I have neva cooked it while I owned it tell me wats wrong im hoping I just blew a gaskit or somthing its has tat get gaskit maker not real gaskits but the worst I fear is ive dropped a piston or somthing pleas tell me wats wrong