Knowing what you want and sticking to your guns_as long as they are reasonable_is great. Especially in a forum where people can be mighty convincing with their go straight to 8x10 arguments. believe me, they are convincing too.
Don't let not having room to tray process stand in your way. I have very little room too. The bathroom is a very easy place to black out and if you have a tub you have a place to process. You will get a sore back though. I built some tubes following Donald's method and they work great. They did take practice though. and no more sore back, or hanging out in the dark for a very long time.
If 4x5 is your route then great. There are lot's of ideas and some really cheap ones too. I got a mint busch pressman D for next to nothing. Be careful before you purchase and make sure you know what you want. Nothing worse that movement envy in the field. and do not sell out monorails that can be broken down and packed that way. Yes longer to set up but everything takes longer with large format. When I made my move up I realized quickly that I had to anticipate the light a lot more. No more skidding to a stop, whipping out the camera and firing off a roll in the last few seconds of a South Western sunset.
For lenses I would go to a camera store and try them on a camera they will let you fiddle with. It helped me a great deal when I was deciding what to buy. Older guys in camera stores are very helpful.
No advice will replace actually laying your hands on a camera or looking through different lenses.
Good luck.