I was crusing my 94 Z28 the other day, and I decided to slam it into wide open throttle... well I did and I heard a slaming noise.. well it felt more like I hit a pothole or something cause the whole car shook.... I did it again, and it slammed again... This time it kinda felt like it came from the front of the car, I could feel it at my feet... but still, the whole car was shaken by it... does this sound like my motor mounts are going out. At normal acceleration it doesnt happen, even when I quickly accelerate it okay... its just when I go into WOT that it slams the way it does...

if it is my motor mounts, how much does something like this cost? Parts and labor?

Sounds like the tranny or motor mount. Motor mounts usually wont break that easy but if I were you I would replace all 3 with poly units. Jegs sell poly motor mounts for 24$ a side and 20$ for the tranny mount. All around 80-85 total I believe after shipping. Labor is something else. I would actually do it myself. If you are not mechanically inclined prepare on spending a good amount on the replacement.

Well my car was recently in a accident to the front end, thats why I had to replace the front end of my car. And I was thinking the impact couldve damaged the motor mounts... not only that but my car has 123,000mi on it. I just got my transmission rebuilt last year. So I dont know if its the trans-mount... but it couldve been jared loose also because the accident I guess.
I like to work on my car but I only do little things... I changed out my oxygen Sensors,my air pump, my ignition coil ang other stuff. I can change my brakes and oil but like I said those are just little things... Ive never worked on something like this though... it seems kinda dangerous if you dont know what your doing... and expensive if you f**k up.

If you do all that other stuff, then you can do the mounts. You just need a floor jack and do one side at a time so that the engine will fall back into place. I replaced my motor mounts with GM stock ones and had to go 70 miles to get them, only to find out that one of them didn't fit. Called the dealership to see if it was the right one and this was a revision GM came out with. Called the local dealership and confirmed the same part number. So I grinded and drilled the holes where the shell clamps (the metal outer shell) and replaced the rubber inside. Clamped the two pieces together with bolts and spot welded the two halves. If you get poly motor mounts this is what you will have to do. As for the trans that is easy.