I have a hard time putting into park

Could be either one, try adjusting the linkage, and look for worn or damaged bushings on the loop ends of the linkage and levers. Here's how:
GEARSHIFT LINKAGE 1. Apply parking brake. On models with C6 transmissions, set shift lever to "D" position. On other models, set shift lever to "OD" (overdrive) position. 2. On all models, hold shift lever against stop by hanging 3-lb. (1.4 kg) weight on lever. Loosen shift rod retaining nut. See Fig. 9 . 3. Move manual lever on transmission fully rearward. Move manual lever forward to "D" position on C6 models, or "OD" (overdrive) position on other models. 4. With shift lever and manual lever on transmission in "D" or "OD" (overdrive) position, tighten retaining nut to specification. See TORQUE SPECIFICATIONS. Remove weight from shift lever. Check for normal operation in all selected positions.

GEARSHIFT CABLE 1. Apply parking brake. On models with C6 transmissions, set shift lever to "D" position. On remaining models, set shift lever to "OD" (overdrive) position. 2. On all models, raise and support vehicle. Disconnect shift cable from manual lever on transmission. Pull downward on lock tab on shift cable at transmission bracket. 3. Move manual lever on transmission fully forward. Move manual lever backward 4 detent positions to "D" position on C6 models, or "OD" (overdrive) position on other models. 4. Reconnect shift cable to manual lever on transmission. Push lock tab upward. Lower vehicle. 5. If shift indicator does not align with "D" position on C6 models, or "OD" (overdrive) position on other models, rotate thumb screw near shift indicator until properly aligned. NEUTRAL SAFETY SWITCH AOD Neutral safety switch is located on side of transmission case. It is nonadjustable. Use Socket (T74P- 77247-A) when replacing neutral safety switch or switch will be damaged. MANUAL LEVER POSITION SENSOR (MLPS) AODE-W/4R70W Install Gear Position Adjuster (T91P-700100A) into slots in area of MLPS on left side of transmission. See Fig. 10 . If slots on sensor do not align with slots on adjuster, loosen sensor NOTE: If necessary, remove steering column covers to gain access to thumb screw for shift indicator adjustment. Ensure transmission operates in all gear ranges with correct transmission detent position.
mounting bolts and rotate sensor as required. Tighten mounting bolts to specifications. See TORQUE SPECIFICATIONS.