The A7iii is a lot of camera but if you can swing it why not?! The menu is deep and broadly encompassing and if you're really interested in learning the camera the curve will be relatively steep but ultimately rewarding. The kit lens (which I believe is 28-70, f3.5-5.6 is very, good. Maybe even very, very good. It's takes a big hit on-line because it's "classified" as a kit lens but I've taken some seriously great pics with it. It's also focus fast and very light. I would not hesitate for a second to recommend that lens especially if it can be bundles as a sale package. I would however warn against the Sony 50mm (which many first time A7 buyers choose for their first lens) as it's simply the most finicky 50mm prime I've ever encountered. It's a perennial focus hunter and stutters and stammers to much to be all that useful. It does take a brilliant pic if you're patient enough to sit and wait for focus. If you wanna take it a step forward in lens's the venerable Sony 24-105 f4 is the best zoom lens I've ever owned and covers enough ground (and brilliantly) to last a beginner years. IQ, color and sharpness are simple outstanding. It is and always will be my "go to" for my Sony Alpha's if a very specific type of shoot (ie: wide angle ect) is not called for.
As to dealers, if you're in the States I've grown to really like
B&H. They've become informative, fast, friendly and efficient. If you happen to be in California I've always had a good working relationship with Samy's. I don't think they as good as
B&H for strictly on-line stuff but they do also have brick and mortar places.