do you know if this is fixable? or the cost to fix it?

I have seen failures with that part before, but never exploded like that! That is your intake plenum that has blown. A new one will run you about $150 at autozone, but you'll also need other parts to go with it so you are looking at maybe $250 - $300 in parts alone, but the good news is it can be fixed.

From the picture I can see that's the series 2 3800 V6 by GM. It is normally a very good engine except for this flaw.

The EGR stove pipe goes up into the intake plenum from underneath, and the problem is the stove pipe gets very hot and will warp the plenum over time. If severe enough, this can cause coolant leaking, and even total failure of the plenum like in your picture. The fix for this is of course, to replace the plenum, but its a little more involved than that. Honestly this is a job for someone who has experience in repairing this type of failure, which I have (dealt with it on about six of these engines so far).

I would also recommend that you get a lower intake manifold gasket set because there are two bolts for the lower intake manifold that can only be accessed once the plenum is removed, and if you were to leave that alone and just throw on the new plenum, there's no telling when those old gaskets will go and you would have to take it all apart again to change them. Also, a new PCV valve wouldn't hurt either. That's a very cheap, but crucial part for this engine.

You'll need at least a new rocker arm cover, but likely more than that. A rebuilt/reconditioned engine swap might be an easier fix. You might want to call around a few local shops to see if they might be able to give you an estimate for your make/model/year. It obviously will require a tow, either to a salvage yard or repair shop.

Its a GM 3.8 v6. Probably an impala or grand Prix. This is actually a common issue with these cars. Its gonna need a lot of engine work