With you already having Gen4 and the HT2000W modem, they may not need to schedule a tech visit for the upgrade, though if they need to change you to the alternate satellite they will.
As for advantages, you may get higher speed and the cost may be lower, both per GB and overall, and there may be higher data plans available in comparison to what you have or can get with Gen4. The largest residential Gen5 plan is 50GB, though that may not necessarily be available at your location.
You can check https://www.hughesnet.com/ to see what plans are available and if there are any current upgrade deals available for your location, but the only way you'll know for sure what it would cost and entail would be to call HughesNet Customer Service at 866-347-3292.
The best advice I can give is, if your Gen4 service works well for you and has good speed, and your price is decent in comparison to what it would be with Gen5, either overall or per GB, or both, and to upgrade to Gen5 you would have to change to the alternate satellite, I'd stick with what you have. The reason I say this is that you never really know whether Gen5 will be better unless you actually do the upgrade, and there is no going back to Gen4 once you do, so if Gen4 is already working well for you, it'd be best to stick with what you already know works well. If your Gen4 speed or service isn't all that great, however, or there is a good bit of money you'd save by upgrading, or even both, which would be better, I'd say go for the upgrade.
For my personal experience, I upgraded to Gen5 back in March 2017, when it first became available. My Gen4 service worked very well, and I was getting far above my plan speed (about 20-30Mbps vs 10Mbps). I upgraded to Gen5 because the new satellite was wide open at the time, and the price was better, and for me it was worth it. I got more data for about the same price, and my speed went up into the 40s, where it still sits today during off peak periods But, it's location, location, location. Everyone's experience varies, and no speeds are guaranteed.
Hope this helps.