Hoping for some guidance as I'm literally lurching along. Last week car (automatic) started having hard shifts. Checked transmission fluid & level was a bit low, but still within range. Color was reddish brown.
Went to the auto parts store to get engine codes read & had the following:

P0705 Transmission Range Sensor Circuit Malfunction,
P0700 Transmission Control System Malfunction
P1457 Evap System Problem(have had this code for a while)
81-1 ABS Control Unit Malfunction

The check engine light has been on for a while due to P1457 code (which I've obviously ignored), but the others are all new within the last month. That was on Weds. Drove only short trips for the next 2 days. Noticed that the shifting was okay until engine reached operating temp-then the hard shifts got really bad. Starts reminded me of learning to drive a stick & having the car leap forward. Stopped driving Friday morning & rented a car for the weekend.
Was planning on picking up a new switch this morning and took the car down the street to get the codes read again (misplaced my notes) and now had 2 additional codes:
61-1 battery voltage malfunction (installed Honda 5yr battery 5/13)
P0740 transmission torque converter clutch circuit malfunction

Did not changing the switch out right away lead to the P0740 code?
Is this still DIY fixable? I'm pretty handy and my set of tools is growing.
I didn't think changing out the switch was a problem - but now am wondering if this is getting beyond my ability.