first, it's always helpful to post year/make/model of RV you have. that way those that own the same model, can be really helpful.
1. if you don't keep the trailer plugged in(you didn't state whether you did or not), then the parasitic power drains can empty a battery in just a few days.
yours may be permanently dead. that's why many of us install a battery disconnect switch.
2. without knowing what trailer you have or what size/brand/model a/c you have, can't say what generator to get.
BUT quiet costs money. if you plan on camping next to others, don't get a cheap generator. no such thing as a cheap AND quiet generator. but the new Champion 3100w inverter generator can be bought for under $900 and will probably run most 15k a/c's and it's nearly as quiet as a Honda.
if you plan on just boondocking or camping at motor races, then a cheaper open-framed generator, like the Champion 3500 can be bought for under $300.
and Zoe the Wonder Dog(R.I.P.)
'07 Roo 23SS pushing an '07 Chevy Avalanche
Equalizer WDH and Prodigy BC