Yes you can. I'm not sure why people always ask "how much" as it's not always going to cost the same, it's not like shops all over north america have a set "rate" as to how much a 20V swap will cost.
Usually depends on the shop or if you do it yourself. Be prepared to pay $2000CDN or more for a Blacktop alone.

Installation, probably another $1500 and up.
Blacktops are not cheap and easy to come by as silvertops are. I've seen Silvertops in the Toronto area go for about $400 for the motor alone, then blacktops for like $1200-1500 just for the motor, then complete for about $2500.