Is it likely that a felony charge of larceny be lessened or expunged for a first-time offender with a clean record?

This is a serious situation for sure.  However, several things could happen in your favor.  Your attorney could try and get the charges (whatever they may be, you did not specify) dropped by the corporation, or reduced to a lower charges by the prosecutor, or he might try and get you diversion.

Diversion, regarding criminal procedure, is a system for giving a second chance to a first-time criminal accused of lesser crimes.  Rather than serve jail-time, those convicted are able to perform community service, make restitution for damage caused by the crime, obtain treatment for alcohol or drug problems if there are any, or undergo counseling for antisocial or mentally unstable conduct.  If the defendant cooperates and the diversion results in progress, the charges eventually may be dismissed.  Diversion is usually a one-shot deal, typically not granted for a second offense.  It allows defendants to escape the stigma of a criminal conviction.  Diversion is not automatic but rather grated at the discretion of the presiding judge.  However the fact that you are a first time offender and this was a non-violent crime is in your favor.

Also note, that in the State of North Carolina, you can get your record cleared by a process known as "expungement".  However only arrests not convictions can be expunged.  If you were granted diversion there would be no record of conviction; then you could have the record of your arrest expunged, effectively clearing your record entirely. 

Of course, if none of these things happens the amount you took ($1,800) most likely puts this act in the category of a felony which, under both state and federal law ( you didn't specify which), is punishable by a substantial fine and imprisonment.