i suggest dont spend much if someone say things and tell u tales unless you know they are pro's..
if you got for service and recharge.. change filter dryer + replace all -o rings and get it vacuumed with proper vacuum pump for good 1 hour... then charge refrigerant purging all air from lineset ....... your best chance of making it give a go and increase performance..
i hope evap is not choked with dust...it can only be checked when you dismantle the whole thing unless it comes with cabin filter