Looking on Machine Finder, the 345s are between $1200 and $3K (there are some for more, but they are dreaming). So, getting the 345 fixed is probably a good idea. There are quite a few threads and videos of people who have done it before. Just replacing the cam and water pump is cheaper than some of the things that people do, because they are already in there and it will never be cheaper to do them (like replacing pistons and rings, boring the block, replacing the valves and/or the head and gaskets). Doing all of those things would give you a near new engine. Your engine has 900 hours on it, so some of those additional things might be a good idea. If you are doing the work yourself, it just adds to the time, but gives you more learning. If you are paying some $60+/hour to do them, it can pretty quickly become more than the cost of a new engine (at least an air cooled one) and cost more than someone else would likely be willing to pay for the machine. I would do a leakdown test on it to see what condition it is in. I did that on my 400 hour X534 and it measures as almost new with only 2% leakage, so there is no reason to take mine apart for a long time.