Amarion58

I been driving with no problem since changing since I changed the timing chain and gears on my olds 307. I nhave to so called master mechanic for a friend that said it was idled for high and I let him lower it or whatever he did and my oil/choke light has been on since then and won't go off. I don't have no oil pressure gauge but I don't think it an oil pressure since it came on right he lower the idle. Any ideas it can be before I spend money on a oil pressure gauge