My gf's Jeep Cherokee 2006 is having transmission problems...?

well it seems its starting to slip... I had an Isuzu Trooper and it had the same issue before it died on me. But this Jeep has like 27,000 miles so its not that bad... and i'm sure this issue is still in it early stages. Any suggestions on as to how i can fix it without blowing my budget on it?