Hi, you need a linear flash and an omnidrive or similar to update the card for the Honeywell MK 5 and 7 cards, other than that it's basically a cut and paste of the files, you can't swap cards/ types
The MK 8 cards are an ATA card so can be done using a normal PCMCIA slot.
All the files are available to download if you have access to them via the Honeywell ADS site, it's also where you'll find any Nav D/B and tech pubs you have access to.
I've not seen any other options loaded to a Honeywell EGPWS and have always used the same database for all the aircraft I work on, but there are a few options listed.
The expensive part is really the omnidrive and linear flash as they work out at around $450 each. I can't comment on costs for the access to the databases.
If you set up access to the Honeywell site and ask for email notifications they update you when they're released, they find seen to update to any pattern and each type is not at the same time.
Hope this helps, what type are you wanting to update?
Mark