Can I upload my waypoints from my 12XL to the 450T and if so how?
Yes.
The 12XL has a serial interface as I recall. I'd download and install MapSource (BaseCamp won't communicate via a serial interface but you'll need to install that first if you don't already have MapSource). Then use MapSource to read all the waypoints from your 12XL. I'd save these in a (GDB) file. Your should then be able to use MapSource (or BaseCamp if you import the GDB file into it) to send those waypoints to the 450T.
