Here's the story, I just moved into a place and the former tenants left a GE side by side refrigerator. Worked fine for about a week and recently the freezer started frosting up.

Went in and cleaned off the condenser; no luck. Checked the evaporator coils and they are completely covered in frost i.e. not patchy so I assume that it is a defrost problem and not a refrigerant problem. All of the fans in the unit run. I am relatively new to the appliance repair world but am handy and can do most all home DIY repairs. I plan on replacing the defrost timer, the defrost heater, and the defrost thermostat in order to cover all my bases and don't have a voltage meter handy.

Here's the big problem: The GOSH DARN model number tag has been ripped off the inside of the fresh foods section. GE says they can't help me period without a model number. I also don't have a user manual or anything like that. By looking over diagrams online I've discerned the model number to be a GSS22JFMWW series or something very close to it. I believe the unit was manufactured in 2001 based on a tag in the back panel that mentions something about oil and nothing else. I've found parts close to what I need for the thermostat and the heater but nothing about a timer. Is this timer integrated into the motherboard?

I guess what I'm asking for is some insight into the situation as far as choosing the right parts and fixing my problem. I assume many parts are interchangeable? Any type of advice that anyone can offer me would be huge. I really don't want to call a repairman if I can do it myself but I'm afraid of causing more damage than I fix.

Thanks so much!!!

Here is the parts breakdown for a JFMCWW, the defrost heater and defrost thermostat should be standard for all this series
Replacement parts for GE GSS22JFMCWW | AppliancePartsPros.com

You did not say what the actual problem is re: food thawing etc.

Checked the evaporator coils and they are completely covered in frost i.e. not patchy so I assume that it is a defrost problem and not a refrigerant problem.
It is normal for evaporator coils to be frosted but it is the amount of frost that is the issue. You have a defrost problem if they are frosted/iced up so bad that the fan cannot pull air through the vanes. The good thing is it sounds like your sealed system is working fine. Sometimes if it is just frost on the back wall it is a bad door seal.

All of the fans in the unit run. I am relatively new to the appliance repair world but am handy and can do most all home DIY repairs.
Here are a couple good links on basic fridge repair
http://www.applianceaid.com/frig.html
Refrigerator Repair Guide: How To Fix a Refrigerator - ACME HOW TO.com

I plan on replacing the defrost timer, the defrost heater, and the defrost thermostat in order to cover all my bases and don't have a voltage meter handy.
I would get a meter, you can get a decent digital multimeter for under $20.00, you do not need fancy. The board is over $100.00 so I would not replace it on a guess.

Is this timer integrated into the motherboard?
Yes.

I assume many parts are interchangeable?
The defrost thermostat and heater will fit many GE's
Check the defrost heater it should be a glass rod. Quite frankly these are crap. Often you can see where it has burned out. This part has been updated to two heater (comes as a kit) each heater is lower wattage than the original but the total is about the same so they burn out less often.
Not a bad idea to also replace the thermostat and it is not that expensive
The control board will be refrigerator specific, AppliancePartsPros might be able to cross reference it with the numbers off the board itself..

if I can do it myself but I'm afraid of causing more damage than I fix.
Not much you can mess up as long as the unit is unplugged when working on it. Following is a good site with some basic fridge repair info.
http://www.applianceaid.com/frig.html

On some GE's you can force a defrost cycle on others you cannot. See the above link. In any case it is easier to check the heater and thermostat with a meter.
GE is a pain to get info on, they like to keep their techs busy. Of coarse I might have a different attitude if I was a GE tech.

Hope the above makes sense and is helpful.