Welcome to the forum and congrats on the new boat!
I'm not familiar with what that particular ladder looks like, but you might post a pic and we can check it out. My local dealership is pretty easy to deal with, and
most things don't take my breath away when quoted. If your source sounds high and you're looking for a sanity check, try Jim at Lake Union Searay in the Everett, WA store. He knows these boats pretty well it seems.
http://www.lakeunionsearay.com/conte...47&cpid=11030&
As far as seats, if you're handy I've read you can remove them yourself, take them to a local upholsterer, then re-install them yourself. I've also also seen complete seat cover kits custom cut by boat in the Overtons catalog, but have no experience with their fit. It might be another avenue.
If you're looking for a quote on a new Bimini, try calling Leta's Top Shop. She does nice work for a reasonable amount and has many of the Bayliner and Maxum patterns that were used in the factory. I've had her do work for me a few times and I continue to be impressed.
She's swamped with work this time of year, so you are likely better off calling her than using the web form.
http://www.letastopshop.com/