[villagetinker]

Not sure why your shower needs to be regrouted, there are much less costly options and sone DIY options.

Our grout was not originally sealed, I did the sealing myself with a product that was supposed to be good for "20 years". Well that did not work, so after several years I came across "Grout Shield" this is a paint like product, and comes as a complete kit, cleaner, tools, and colored sealant. We chose to keep the same color as the original grout, and they match it so close that I actually missed a few areas, which I found the next time I mopped the floor. I just touched of the missed area. I think we are going on 5 years and ground looks very good, but does still need an occasional cleaning in the heavy traffic areas.
Lowes sells similar Mapie products, but I have never used these.
My point, I did the entire tiled area of our house (no bedrooms or closets these were carpeted), and both bathrooms and the shower, took around 2 weeks 3 or 3 hours every other day, and probably save hundreds to a couple of thousand dollars. The kit was $60.

Now if your grout is actually cracked and falling out, then the above is not a good solution, however my stepson who has done tile installation indicated grout removal and replacement is a time consuming and dirty project.

I hope this helps, feel free to send a PM if you would like to discuss further.