Sound like your mechanic is not to good with electrical issues.

One: the D4 in your dash, is a single bulb which I have herd costs about $15 bucks to replace. Mine went out on both tegs i ownd and on my sisters in laws also. Here is what i did. Take out the insturment cluster (look for a DIY thread on installing gauges). Then take the bulb from the D1 out and replace it with the D4. When was the last time you had it in D1? So no biggie on having the burnt one in D1.

Second: if your shifter bulb was out then change the bulb if that wont work, try a different bulb since these bulbs are a two pack 99% of the time when bought at an auto parts store. Then also try taking a volt meter and seeing if there is even power coming to the socket. If not then start looking at yr fuse boxes for a blown fuse.

Ask you mechanic what he fawked with in your car, and put it back to normal