1994 Chevy Camaro motor, transmission, head gasket?

Not sure what is up with my car but it has been doing all sorts of funny things. I know it has a coolant leak and due to that I think I may have blown a head gasket for the simple fact that I just filled it up with collant and now when I start it, it blows white smoke from the tailpipe, but only for a few seconds or so then it quits. It also has been leaking transmission fluid. I was not aware that I ran it for about a week or so with no transmission fluid until it started not shifting right, then I checked it and sure enough it was completly out. Some days it runs great, others not so great. Some times the battery gage will go up and down and so will the oil gage. I'm just not really sure what to do with it. I'm thinking about just putting a new transmission in it, but I do not know if I should go ahead and do a motor as well.