Not quite THAT simple...
You said, I like it that I can use my existing bowl and hose systems. Just add the pump, problems solved.
You'll also be replacing the base, which won't match the mounting bolt holes for your current toilet. So that will require drilling a couple of new holes and filling the one(s) you won't use. The good news: it's not that hard to do. Toilets are mounted using lag bolts, so just back 'em out...no nuts to deal with. A little epoxy filler, some touch up paint...
And you'll prob'ly need some new 3/4" hose...'cuz the intake fitting is on the FRONT of the PHII/PHC pump, requiring about 3" more line than a fitting at the rear (which is where most of 'em are). You'll need a vented loop in the intake too (necessary for all manual toilets and most electrics that use raw water)...it needs to be between the pump and the bowl, which will also require enough hose to put it at least 6-8" above waterline AT ANY ANGLE OF HEEL...which, on most sailboats puts 2-3 FEET above the bowl.
And finally, if the hoses are anywhere near as old as your toilet--or even anywhere near 10 years old, you need to replace ALL the hoses.
Do it all right the first time so you won't ever have to do it over.
So there's just a WEE bit more to installing it than just "plug and play" set 'er down and put your bowl on it.