I agree that you should find out as much as you can about MGUS. This will help you prepare questions for doctors when you seek a second opinion. Here are 3 websites that talk about MGUS in plain language:
- MGUS Mayo Clinic https://www.mayoclinic.org/diseases-conditions/mgus/symptoms-causes/syc-20352362
- MGUS to Myeloma: Study Suggests Risk of Progression Can Change (NCI) https://www.cancer.gov/news-events/cancer-currents-blog/2019/mgus-multiple-myeloma-progression-risk
- How Serious Is Monoclonal Gammopathy of Undetermined Significance (MGUS)? (healthline) https://www.healthline.com/health/how-serious-is-mgus

I might suggest reading them and returning here if you have questions. Fellow patients will be happy to share their experiences. And share with you questions you can ask the doctors.

Where to get a second opinion depends on a number of factors. Choose a large cancer center with expertise in hematological cancers, like Mayo Clinic. The other factors are personal. You may need to consider your insurance coverage, your financial and mobility ability to travel, or a preference to stay close to home.