[alamy]

Hello mighty forum guys
Please help!- I have no idea about anything (I am a widow and inherited the P38- RR 2001 HSE) so pls. don't tell me I'mdumbo (actually you can tell but is of no use)...
sequence of events:

1. had a major coolant leak through the expansion tube (afterward, I came to the conclusion/presumption that the cap was not tightened properly when I added coolant since right now- after refill- there is no visible loss anymore)
2. had to change the battery (did a by-pass so I don't lose the BECM codes); new battery is Group 31 12-Volt Commercial Battery, 950 cold-cranking amps, 1170 cranking amps, 175 minutes reserve capacity (so I assume is good for P38)
3. at first drive after battery change I've got "service engine soon"; a neighbor checked the codes for me before I go to a mechanic
   
4. told me he got 2 codes:
   
5. P1667 (powertrain fault? according to his reader)- on the forum I found P1667 is "Engine anti-theft signal circuit low Serial link short circuit to earth"
   
6. P055 (also, as he told me- loss of cooling fluid; could be related to the recent leak that was registered/remanent in the computer?)- OK, since there is no such code I assume is/he meant either:

• P0505 Idle control system malfunction Blocked IACV - high or low rev/min error
• P0155 O2 sensor heater circuit malfunction (bank 2, sensor 1) Front sensor heater RH bank - short/open circuit
• P0550 Power Steering Pressure Sensor Circuit Malfunction
  

Now, the question is: are these computer malfunctions/gremlins after the battery change without resetting the computer?
How bad am I standing, you think?The way it seems I have 3 choices and I ask your opinion, guys:

1. try to disconnect the battery to reset codes & clean the connectors (which hasn't been done when I replaced the battery, mea culpa)
2. go to a cheap mechanic that I know (who doesn't know much about RR specifically) and see... (he will offer to clear the codes, probably, but it might be a good idea or not...)
3. go to the dealer- which will kill me...(I am low budget, shops take advantage of widows big time-ie. last oil change cost me $500...- and I am not sure a 2001 car is worth it anymore)

I also have to mention that the oil(synthetic) is pretty old by now (about 3 years) but 3 people told me it still looks OK since I drive about 1000K/year (that alone should tell you something about me and my RR...)
Any suggestion is appreciated! (might be that I don't make much sense with my story to ¯\_(ツ)_/¯you so ask me anything)
Thx.