hardwire an inverter?

I recently installed a Samlex 1000w inverter in my 5th wheel. I ran 4ga wire directly to the battery using a 150a fuse. I then ran some 120v house wire wire to 3 separate 120v outlets. I placed one near the tv, one near the entry door, and one in the bedroom. I also bought the remote start switch. It shows the current volts from the inverter. It simply wires in with an Ethernet supplied cable. While it was a tricky job sometimes finding a decent routes for the 120v wiring, in the end it all came out clean. I bought some white surface mount 120v boxes at Home Depot. The 5er has brown 120v boxes as stock. Having the white ones helps the wife figure out whether we're on shore power or battery power:). I have two original 3 year old 12v 24G batteries. I can run everything except the micro, AC or coffee pot. It' overkill for what we run off the batteries as far a charging things or using the XM radio. It also runs a clock for nighttime in the bedroom.
To the OP you don't want to just tap into your RV wiring. Hard to tell how well it's run or how much you can safely pull from it. It was pretty easy to just tap into the house batteries.