Why does my bike feel slow, hard to ride and wobblier now?
If your headset was replaced due to crash damaged, well that's a pretty intense crash. I'm going to assume they adjusted it. They also adjusted your brakes. My guess is your problem is two fold:

1) The headset is adjusted too tight, making the bike feel like you have too put too much input into it to turn, and when it does it happens all at once. That would give a wobbly feeling.

2) Check to make sure your brakes are not touching the rim, nor are too close to the rim (less than 3 mm from rim to braking surface). The drag will make you feel like you are constantly pedaling harder.

Good Luck!