Did you charge the replacement battery you got?

New batteries, contrary to belief, do not come with a full
charge.. and if they've sat on the shelf of the parts store
very long, who knows how much of a charge it has.

Before you go looking at the starter, I'd put a trickle
charger on it over-night(12hrs) and see if that solves your
problem.
Also, be sure to check your battery cables for corrosion,
loose grounds, etc.. make sure your cables are all tight.

Then, if you still have a problem, start looking at the
starter.

1995 Trooper LS auto 3.2 DOHC /w SOHC intake
1989 Trooper 2.6 auto
1989 I-Mark RS DOHC 1.6
1991 Stylus XS DOHC 1.8