Either the Marantz or the Yamaha would be fine. I would opt for the AV 7705 if you are planning to update to 4K. Any pre/pro is now going to have more channels than you need for your system.
I see one problem that I did not note before. I looked up
the specs of your projector and it does not have an HDMI input. We are now past the analog sunset and new gear will not output an analog signal from and HDMI source by law. So I'm afraid that projector has to go. So you might as well upgrade to 4K since making this change is mandatory for you. Sorry I missed that, but was not familiar with that projector. The RSP 1068 I am very familiar with as my late father had one. In its day a fine unit.
As far as doing it yourself, it is a matter of plugging everything in correctly. I hope you can run an HDMI cable to the projector. Hopefully the installer ran the cables in conduit. If not you may have a major construction project on your hands. I have all cables in conduit. This is the way it should be but usually is not.
When you change the pre/pro, then all the cabling will be different except to the amp.
Run all your source units to the Pre/pro with HDMI cables, and one HDMI cable out to the projector.
How far is it from the pre/pro to your projector? If it is further than 25 ft, then that can be a problem.
Really this is a job you can do yourself, unless you have to open walls or ceilings to change the projector.