Your model number looks short a couple digits, so I used GHW2 they will all be very close to each other.

Here are your parts
Replacement parts for FRS26ZGH models | AppliancePartsPros.com

Here is a wiring diagram
http://manuals.frigidaire.com/prodinfo_pdf/Anderson/218909400.pdf

First remove the evaporator cover in the freezer so you can see the coils.
Do not let them de-ice.

Manually force a defrost cycle by turning the defrost timer cam (Item 23 in Section 5) 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 14 in Section 6) 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 21 in Section 6) 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.

supresmooth
[COLOR="DarkRed"]
The freezer gasket seems a bit wonky on the bottom inside corner, Is that really a likely culprit? Should I try replacing the thermostat anyway/first?[/COLOR]
The gasket could be the problem especially if you live in a humid part of the country.
Take a 2 inch strip of paper and place it between the door seal and the frame then pull it out to see if it is sealing correctly. Works your way around the door checking every 6 inches or so.
A common problem is the seal grabbing and twisting on the hinge side. A light coating of vaseline or white lithium usually fixes this.
Could also be the thermostat. Get a thermometer and monitor the freezer temperature.
I am assuming you mean the main thermostat and not the defrost thermostat.

[COLOR="DarkRed"]I am worried about a freon issue, as I definitely can't afford a new fridge right now.[/COLOR]
I am very doubtful that it is a freon problem, wrong symptoms for this.
Low freon will cause the unit to run either continuously or a lot more than it used to.

Glad to hear you have it fixed.
And thanks for getting back to us. Now when others search for a similar problem they will see what actually worked instead of just suggestions about what could be the cause.

For future reference.
You could have used a couple wire nuts to connect in the defrost thermostat.
I like to used the hard black plastic (bakelite) type as the have more temperature tolerance.
Keep the wires long enough so that you can attach them over to the side and so that the wire nuts face down (stops water getting into them.
Some follks also like to seal them with some silicone as an extra protection.