It's a pretty massive kit. The part I hated was the External Tank, because it (mine, anyway) was a mother to align because the plastic was slightly warped and this caused all kinds of grief with making it look seamless. The blown-on foam coating ended up being a mess around the seam, and I eventually figured out a way to fix it using auto surface filler and (I think it was) 180 grit sandpaper to press into the still soft filler, to give it the texture.
Still, despite the usual flaws with a kit like that, it is a darned impressive monster on the shelf.
Just work through the pain, as Dad used to say.
There is a company that makes full body decals for the various shuttle scales, including 1/72, that incorporate virtually every feature on it, including the color differences in the weathered tiles. You paint the shuttle the basic colors, and then wrap it in the decals. If my senility abates, I'll post the name of the company.