Run, don't walk from that dealer/contractor.

A new condenser should never be installed without a matching evap coil. I recommend you make the switch to an R-410 condenser 13 SEER model.

IMO

Does this contractor really think your 35 year old coil will not begin to leak after installing a new condenser? This is going to cost you much more than $1800 if you go with this guy.

Holy Moley! Dude 35 years? You got your moneys worth twice over! Do not try to repair this system-it has served well and it is time for retirement. Yes a new system will cost, but that is the cost of being alive. A new system will begin saving you money immediately on energy costs. I know finances can be tough but there has to be financing options available. You would be better off spending a couple of hundred dollars on window units than spending $1800, then spending another $3000 to replace the air handler next week. Get creative and find a way to finance a new system. Your old one has served above and beyond.

Thanks for the responses. Looks like I'll be getting an R-410 condenser + coil.