As PastorGray pointed out the proper way to read the pairs for a mobile or portable is the first set is your RECEIVE frequency and the second number is your TRANSMIT frequency sometimes indicated by a + or -
The other thing that you will need to know is the tone coded squelch (CTCSS, PL, etc) or a digital squelch (DCS) which may or may not be used. If it isn't being used you will usually see CSQ or nothing at all. So 462.5500 + / 141.3 would indicate that you set your mobile / portable to a receive frequency of 462.5500, transmit to 467.5500 and tone squelch to 141.3. You can elect to use a transmit tone without a receive tone if you wish but in order to access the repeater you would be required to use the transmit squelch. If you do not put a receive squelch in you will receive ALL other repeaters and maybe even simplex (users talking on the output) of the repeaters in your area. I usually use both a transmit and receive tone on my mobile and portables.
The scan question is going to be radio specific. I haven't seen a radio built in the past 10 - 15 years that doesn't have a scan feature and the ability to "lock-out" channels that you don't want to listen to. Many modern radios will have the ability to create one or more scan list and even automatically scan an the list when you select a specific channel. Some will also allow you to transmit on the channel that is active even if you're tuned to a different channel. EX: if you have built a scan list of the GMRS repeaters in your area and have elected to associate that with channel 1 in an auto scan configuration - When you tune to channel 1 your radio will automatically go into scan mode of the scan list. If someone is talking on channel 6 you MAY be able to talk to them on channel 6 without changing your channel selector if your "hang time" is long enough and YOUR RADIO ALLOWS this. If this is an important feature for you be sure you look at the radio specs.
W4ATN / WQMM-856