As far as I know the slant six was allway's a good little motor . I've known a few of though's motors to go 300,000 miles without a rebuild . Now for how hard the head gaskit is to do . That realy depend's on your mechanical skill's . There realy not that bad to do but you have to be prepared for thing's like rusted exhaust bolts and such . It's mostly labor intencive and if you do decide to do the head gasket then I would send the head out to have it resealed while you have it off .
ive already got the valvecover, intake/exhaust manifolds off already, its just i dont want to fix if its a problem with the slant 6 engines. thank you for the reply