Here are your parts, I used the BA unit
Replacement parts for TRX22PPDA models | AppliancePartsPros.com


First remove the evaporator cover in the freezer so you can see the coils.
Do not let them de-ice.
If they are heavily iced/frosted over you have a defrost problem.

If yes.
Manually force a defrost cycle by turning the defrost timer cam (Item 257 in Section 4) till the fans and compressor turn off.
Now check the defrost heater to see if it is on.
Be careful you do not want to burn your fingers.
If the heater is on then the timer needs replacing, re: it is probably stalling during it's rotation so is never getting into a defrost cycle.

If not on.
Unplug the unit.
Remove the wire for one side of the heating element (Item 230 in Section 3) from the wiring and measure it for continuity, usually around 20 ohms or so.

If the heater is OK
Remove one wire to the defrost thermostat (Item 240 in Section 3) and measure it, should be 0 ohms when frozen. Note that it opens just above freezing so must be frozen to check it. Also inspect it, if it is bulged at all replace it even if it measures OK.

If both the above are OK then odds are the defrost timer contacts are toast.
Best way to test this is a live test to see if you have 120 volts across the heater/defrost thermostat combo.

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.

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

[COLOR="Blue"]The bottom heater is visible, but I can't seem to locate the wires, should I defrost it with a hair dryer?[/COLOR]
Yes, if it is that badly iced up you will have to defrost it just to get to the heater's wires.


[COLOR="Blue"]Now since the heater is not working (or I assume), how do I measure the heating elements. Is the heating element the coils or the heater itself?[/COLOR]
Heating element is the heater itself. The coils usually refer to the evaporator coils through which the freon runs.
The heater has a wire coming from each end just disconnect it and measure between the wires.
Be sure to have the fridge unplugged when you do this.
If it is OK, then check the defrost thermostat. Since the coils are defrosted you will have to hold the thermostat on an ice cube to check it.
[COLOR="Blue"]
What colored wire should I measure (FYI I'm a novice at this).[/COLOR]
I do not know but once the unit is defrosted it will become self evident.

[COLOR="Blue"]I defrosted all the ice. Now how do i use the meter? What wire do i remove from the heater itself; any or a specific one?[/COLOR]
I would remove both wires.
If your unit has the same heater as the BABS unit Item 230 in Section 4 unplug it and measure it. Note that it has the defrost thermostat built into the assembly so you will have to hold the face of the thermostat on an ice cube as it is only closed (0 ohms) when frozen.
[COLOR="Blue"]
How do i test it using the meter?[/COLOR]
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.

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

[COLOR="Blue"]What sort of reading am i suppose to get?[/COLOR]
The heater is usually around 20 ohms and the defrost thermostat 0 ohms when frozen.

[COLOR="Blue"]Also a seperate questions about the meters, does the red wire go in the ohm and the black in the comm?[/COLOR]
Yes.
Then short the meter leads together to see what 0 ohms should look like.