I appreciate it. The model number starts with RGDG.
Serial: DF5D302F069602895
The DF indicates Honeywell VR8205H with United Technologies 1012-920 with remote sensor.
The Rheem part number for the integrated ignition/blower board is 62-24044-81
The igniter is 62-22868-93
Flame sensor is 62-23543-01
I strongly urge you to install a carbon monoxide alarm, and a gas leak alarm , if you do not already have those. This is a fairly complicated machine, and the consequences of screwing it up are severe.
You would be better served to put some logs in your fireplace, or use some portable electric heaters, until you can have this checked out by someone who is skilled in repairing these.
On line, it looks like around $300 for the board, $30 for the igniter, $10 for the flame sensor.
I should add....for this type of system, the system ground is critical to operation of the flame sensor. You could check for good ground connection at the wall plug, solid plug, look for loose ground wires or screws in the unit.