If you have a backup then 4000 is expensive, however, I'm surprised at that cost and it's not the sort of thing I would do, I prefer to do it on an hourly basis which includes travel expenses, hours worked etc. some companies do not like an open contract but you have to look at a number of scenarios.
The company/person does not know what the issues will be until a visit to site for example, has the PLC just lost it's program because of a flat battery, is it a fault with the hardware (very common on SLC like processor, rack, PSU).
Is the backup you have readable, is it the correct one and up to date. so many issues. I would shop around for a better deal. You will need the software for SLC (RS Logix 500), a cable which depends on the processor, it could be 232, 485 or ethernet some have more than one port. that version may not work well or at all on Win10 PC, also it will depend on what version of software used to create it (cannot remember what the old dos version was, believe it was APS).