Get the 300 cc Zodiac it has reverse I have 3 they are a great trike for the price.My wife loves her red one hard to get her off to service it like changing oil and ail filter checking chain so forth LOL
I think I mention to you on another site it's better to by the water pump as a whole unit buying them in parts you are taking chances of your old casein is good. between the parts and whole maybe 5 bucks.
It sounds like you shift linkage is out of adjustment. but what you may want to try shut off engine then put into forward or reverse which you want and start engine it will fall into gear. I use this all the time never any noise just goes into gear
I found my 2 on e bay a white and a black with a back rest. As far as the pegs you are on your own I am 6 foot never needed any thing like that. but if you do post what you found. But remember there is a great deal if plastic so you will need to remove fine your pegs add to frame cut open the area needed to clear your pegs good luck.