i think its strange that your ecm was the problem in the first place.. you couldnt get your lights to turn off right? i dont think the light circuits go anywhere near the ecm
abs has its own separate computer as far as i know.. and yea i would find a shop you trust to do the abs i bet it will be cheaper... isuzu quoted me 3,000 to fix my abs.. ive been driving without abs for about 4 months now.. and fixing the problem will have costed me a grand total of about $115 (100 for the part and 15 for brake fluid to flush the system) and if i were to take it to a shop to have the part put in... id guess it would be under 100 bucks for the install... so $215 compared to $3000