I work in autocad 2000 but, if ALL your text is extremely similar, justifications etc., you can use SSX from express tools to create a selection set of the text you want to change, create or insert one piece of text with your new font and MATCHPROP previous.
if they don't call it SSX anymore:
(setq ss1 (ssget "X" '((7 . "LCC"))))
should get a similar selection set.
then create the similar style with ariel font type and name it something different, like LCC1.
then modify the text entities with SUBST and ENTMOD.
but the lisp might look like this:
(defun c:foo ( / ss1 count)
(setq ss1 (ssget "X" '((7 . "LLC")))
count 0
)
(repeat (sslength ss1)
(entmod
(subst '(7 . "LLC1")
(assoc 7 (setq ent (entget (ssname ss1 count))))
ent
)
)
(setq count (+ count 1))
)
)
of course, if you have text in a block, like your title block, the lisp gets more complex, or you can explode your blocks with text in them, foo them, and redefine the block(s).
hope this helps.
roy