Yeah it will work with 4.3 (working on a curve with 4.3 here and will work with pretty much everything that supports SPP profiles via bluetooth and can run navigation software).

Realistically you will probably never need to replace the battery (unless you use the GPS units for 10 hours a day, every day for a few years). If you do ever need to replace it though it is attached with a connector/plug rather than be soldiered so it is fairly easy to replace.