Hey WM...
I upgraded my last house from 100 to 200 for about $700. Our local power company had a deal that if you upgrade service, they would bury new cable for you, remove the masthead on the roof, old line, etc.
I upgraded with a "Cutler Hammer panel" and had an electrician do the work. It took him one day to tie the panel in and get everything working. Following this, the power company came out and upgraded the service.
If you already have a "modern" panel (i.e., after 1985, roughly speaking) you might be able to reuse the breakers and save some money. I did this on my upgrade and it worked great.
Some power companies also have "package deals" listed on their websites for upgrading service, including new panels. You might want to check them out.
Gotta go -- "Gaston" is less than 20 miles from Beach Town and it's already starting to blow. Seems like every tropical storm this season is trying to hit VA Beach.
Andy