check engine light/abs light on

Hey guys. I just bought a '95 GA GT 3.1l v6 with 149k miles, about 2 weeks ago. I noticed when backing up when I leave in the morning the check engine comes on and then when I go forward it goes off after about 5 seconds. It usually doesn't come on till I start to back up. It also comes on once in awhile while driving in town or on the highway. It appears to be usually when slowing down. Then it goes off almost right away. Also tonight when I left for work the ABS light came on and stayed on. Does anyone have any ideas what could be causing these two things. It does lope a little sometimes right after I start it. Other than that it has been running really good with good mpg too. Any help would be appreciated. If I do take it to like an autozone what do they charge?