The difficulty with doing serious mechanical work on anything built in the last 10-15 years or so is due to the electronic controls and extensive use of computers. They are not difficult to work on but the problem is finding the fault so you know what to fix.

You can save serious money by doing your own work, even simple stuff. I can do a brake job in 2 hours or so for $25 or less and a garage will generally charge over 200.

If you have an official shop manual you can do practically any repair that is required.

I have been driving my MG for 10+ years and have never had it to a mechanic. I don't keep a record but I would guess that I have saved enough by working on it myelf to buy 2 of them.

You do need to treat it as a hobby and you have to be willing to spend the time and get dirty. But it is a hobby that will pay for itself very rapidly even if all you can save is labor costs. The last time I looked garages in my area charge anywhere from $50 to $75 per hour for labor. This means that you can have a rewarding hobby that pays you $50 or more for the time you spend on it - a pretty good deal.

Your dad gives good advice if you want to work on a car to learn. The mid to late 1970's MG and Triumph are very simple machines, do not require a lot of special tools and they are somewhat classic. The advantage (for me) of an MG is that there is a merchant in the US (Moss Motors - they have an online catalog) that sells practically anything you will ever need for MG at reasonable prices. Don't know about parts in the UK.

Edit:

Note that front wheel drive cars can be a real challenge. Front engine/rear drive is much, much easier and old type 1 VWs are extremely easy to work on - you can remove the engine with 4 bolts and a floor jack (or strong buddy) and carry it to the work bench.