Jeff, failure to change coolant on a regular basis or to maintain the chemistry can have serious consequences so your plan to make sure the system is clean and contains the right coolant is definitely the correct way to go.

I have not seen or heard the issues that were somewhat common with the two cycle engine such as plugged radiators or silicon drop out, but because of the emphasis on proper coolant maintenance I suspect we still have those concerns, but most importantly the biggest concern is the failure of the cylinder liners due to improper coolant chemistry. The liners can literally become perforated.

Protect that new engine. and the old one as well.