95 Cutlass Supreme Trans problem

Hi
I have a 95 Cutlass Supreme 3.1 liter auto trans. 86,000 mi
Background
Not sure if it's realavent or not, but I had some work done recently (1-2 months ago) to my engine. My low coolant light came on one day and I added coolant. About a week later it came on again and I decided to have my oil changed, as it was about time anyway, and let them see if they noticed anything. My engine oil looked like chocolate milk and had sludge in my engine. It turns out I had antifreeze mixing with my oil inside my engine. Had a mechanic check it out the next day and he changed my lower plenum gasket and tried to get all the water he could out of my engine. Fine. About a week or two later my temp gauge was running hot and my vents in my car gave no heat. So I took it back to my mechanic. Turns out this time it was a small coolant line had a bad "O" ring (leaking) and he replaced the metal part it was hooked into that was screwed to my engine (note: this line starts behind my engine). He said it wasn't building up enough pressure (due to the leak) so thats why I couldn't get heat. Fine. Well now my coolant seems to be staying lower and my light has come on once or twice after this, but I don't see any sludge in my engine when I take the cap off so I'm not sure what to make of it. By the way there is no pools of anything on the ground where I park my car.
Problem:

Anyway onto my new problem.
About 2 weeks ago I started hearing a noise that resembled a baseball card in a bicycle wheel spoke coming from my engine. It seemed to go away when it warmed up, and sounded fine therafter.
I was driving yesterday and I heard something snap. The car jerked a little and I pulled over. I got out, checked my tires, and under my hood. Nothing looked unusual and my dash lights and temp gauge were fine.
I pulled back onto the road and I can't get past 40mph with the engine pushing 6000-7000 rpm. So I drove gingerly home with my hazards on. I tried to shift through 3,2,and 1 to see if that would work better, but it no luck. So now I'm trying to decide if I should junk the car and put money elsewhere or try to save it. I have an appointment with a trans shop that was reccamended to me by my mechanic, but have to pay 95 dollars or so to tow it there so he could give me a quote.
I'm frustrated.
Any advice?

Sounds like a tranny problem. Be advised a rebuild will cost $1,000 to 1,400.

The rest is your call as to wether this car is a keeper or not!!!

I just talked to a guy I work with and He says it could be a bad CV joint. Does this make sense?

CV joint should not slip and let the engine speed as if the tranny is slipping and hold you to 40mph. You could drive any speed as long as the joint hasn't come apart yet. It would either keep making noise regardless of speed or come apart and disconnect the front wheels from the tranny. A CV joint would not slip, allow you to over rev the engine and continue to drive the vehicle. The knuckles are either locked together or not at all and the vibration would be as great as driving with a flat tire if it was even remotely held together. You would coast to a stop if it came to the engine over reving. I have driven vehicles with bad cv joints and even had one come apart while turning a corner. They typically pop and crack for several days before they totally give out. When they fail, it is all of a sudden. It will also not get better the more you drive it. They only get worse.

You could look under the vehicle and see if the boots on the joints are damaged and leaking grease. If a joint is coming apart it will typically rip a boot.