A model number may help other help you.

[COLOR="Blue"]
Question...what is the most likely thing that got fried when i tripped the breaker.[/COLOR]
The most likely is the control board if this unit has one but the voltage spike can take out just about any part.

[COLOR="Blue"]Where do i start checking/replacing parts?[/COLOR]
Cannot say.
Need a model number so a wiring diagram can be found and referenced.
You will probably need a multi-meter.

[COLOR="Blue"]Still start with thermal fuse, cut-off, thermostat?[/COLOR]
I am not sure what the above question is.
If a fuse or cut-out blows it disconnects the parts so if the hum is from the motor then it is not either as the motor is getting power.

[COLOR="Blue"]Surely that didnt fry the motor?[/COLOR]
Again I cannot say but a humming motor usually means a blown motor if the motor is getting 120 volts.

Here are your parts
Parts for Whirlpool WED5500XW0 Dryer - AppliancePartsPros.com

See the attachment for the tech sheet.
Read through it before starting.

First I would try manually turning the drum in the correct direction. It should turn fairly easily.
If OK
Since this was a dead short I then would check the power to the unit.
Try flipping the breaker off/on slowly a couple times.
Check the voltage at the plug
L1 to L2 should be 240 volts
L1 to Neutral and L2 to Neutral, both should be 120 volts.
If OK
Unplug the unit and check the wires at the terminal strip in the machine to make sure none are loose or burned out
If OK
Check the power at the terminal strip.
Do this with the unit off and then when you try to start it.
The L1 (black) to the Neutral (white) is the half of the line for the motor.
[COLOR="Red"]Be careful as 240 volts is lethal !!![/COLOR]

If the above is OK
Unplug the unit.
Set your meter to the lowest resistance scale (usually 200 ohms).
Short the wires together before starting your tests to see if there is any zero offset in the meter.
The door must be closed.
At the control board check from P9-1 to P8-4. This should be a couple ohms re:the run and start windings of the motor.
then check from P9-1 to P8-5. This should be infinite ohms.
If not then the centrifugal switch 5M/6M is closed. Could be that it's contacts are welded together. Therefore the start winding is not in circuit and the motor will just sit there and hum.
If the above is OK.
Then check the motor windings, see Test 2 in the tech sheet.

You will need a multimeter also some experience working with electricity.
240 volts is very dangerous.

If you do not own a meter, I would suggest you purchase a one. You can get a decent digital multimeter for under $20.00. You do not need fancy though it is nice if the leads are a couple feet long.
If it saves ordering one unnecessary part it has paid for itself and you end up owning a useful tool.
Most places will not let you return electrical parts so if you order it, you own it.
A couple things to watch when measuring ohms and continuity
1. Always remove power from the machine otherwise you could blow your meter.
2. Always disconnect at least one side of any device you are checking. This eliminates the possibility of measuring an alternate/parallel circuit path.
3. When checking for closed contacts and continuity use the lowest scale (Usually 200 ohms). Then try higher scales. This scale is 0 to 200 ohms so if the device you are measuring is 300 ohms this scale would show an open circuit which it is not, you are just measuring outside the scale's dynamic range.
4. When you start always short the meter leads together. This will tell you that the meter is working and if there is any 0 offset.

There is a good STICKY at the start of this forum about it's use.

Thanks for all that, about to get started, if the centrifugal switch is welded together can i just replace it?

Ok, the dryer works if i give a push on the drum while holding start, i can then let go of the start button and it keeps running