1990 Chevy Lumina How to Change the starter

Take it to a shop. Its not an easy chore. I have a 92 z34 and they had to drain the radiator "had to disconnect hoses", drain the oil "cuase you have to remove the filter", disconnect the engine oil cooler "simply in the way", all this just to get to the 2 yes 2 bolts that hold the starter in place. All in all, it took them just shy of 4 hours to do it. But, your 90 may be different. Climb under, see what is in the way. If you can get to them, remove the 2 bolts holding it in, the rest is easy.
Oh, make sure to disconnect the battery first, or you'll get an afro. There is a step by step instruction at autozone. Com. May take a minute or two to find it, but very usefull. Should help you decide whether to do it yourself or not. Alot of guys on here will say its easy to do. But what is your experience? Do some research.