Bliss is the tracks/carriage, not the frame. Lenni only goes on the standard frame (which can possibly be Blissed if it isn't - I'd contact APQS and ask first - mention the year of the machine), not the larger Deluxe frame that the 26" machines go on. Bliss is a smoother handling contact between machine carriage and frame and much nicer.
An older Lenni has a 20" throat space. The newer ones are 22".
I've quilted on both a 2013/14-ish 20" Lenni and a 2019 22" Lenni, both with Bliss, and both were lovely to use.
That said, as a 2007 I would definitely check with APQS to see if electronics are still available. I recall a recent post on the APQS FB page from the owner of an older Millie (maybe 2001-2004 era), and certain electronics were no longer available and the Millie couldn't be repaired.